The Fall of Icarus and Kepler’s Camera Obscura:
The Theme of Forbidden Knowledge in the
Sixteenth and Seventeenth Centuries Revisited.
Raz Chen-Morris
Bar-Ilan University and The University of Sydney
chenraz@mail.biu.ac.il
2
The Fall of Icarus and Kepler’s Camera Obscura:
The Theme of Forbidden Knowledge in the Sixteenth and
Seventeenth Centuries Revisited.1
Thirty years ago the distinguished historian Carlo Ginzburg published an
essay entitled “High and Low: The Theme of Forbidden Knowledge in the
Sixteenth and Seventeenth Centuries.”2 In this provocative essay Ginzburg
traced the formation, persistence and change of certain cultural prohibitions on
the investigation of the heavens throughout the Middle-Ages to Early Modern
Europe. Ginzburg’s point of departure was the Vulgate mistranslation:
Noli altum sapere, sed time, of St. Paul’s admonition against human pride
.3 The erroneous translation, according to Ginzburg,
turned the moral condemnation of pride into an epistemological prohibition on
the inquiry of higher things. In many cases, this was taken literally as indignation
of studying the heavens. Ginzburg traces the prevalence of these sentiments into
the sixteenth century. Thence, with the advent of the printing press the ancient
apprehension of astronomical inquiries adopted a new popular display. In the
literature of emblems from the 1530’s onwards the figure of the falling Icarus
1
This paper is part of an ARC supported project, The Imperfection of the Universe (DP0664046).
2
Originally appeared in Past and Present, 73 (1976): 28-42, rep. in Carlo Ginzburg, Clues,
Myths, and the Historical Method, trans. John and Anne Tedeschi, Baltimore: Johns Hopkins
University Press, 1989: 60-76.
3
Epistle to the Romans, 11:20.
3
came to represent the danger and folly of astronomical inquiries.4 The new
science of the second half of the sixteenth century, however, reshaped these
sentiments and anxieties. Ginzburg points to a radical change in the values
associated in the emblems’ literature with the figure of Icarus. In the seventeenth
century Icarus’ curiosity was vindicated and embraced as a positive value. The
medieval religious prohibitions were transgressed, and instead of the warnings
of human curiosity, a new slogan “dare to know” was celebrated.
This paper concentrates on filling two gaps in Ginzburg's captivating
account. These two gaps appear in two crucial points in Ginzburg’s longe durée
history of curiosity: The one is concerned with the emergence of the
epistemological twist to the moral admonition against pride in patristic
literature, and the other appears at its decline, with the emergence of a new
mentalité of scientific curiosity: how can a mistranslation have such lasting
cultural and intellectual effect? What was there in the culture of late antiquity
4
The denouncement of curiosity is usually associated with a moral prohibition and religious fear:
cf. William Eamon, Science and the Secrets of Nature: Books of Secrets in Medieval and Early
Modern Culture, Princeton: Princeton University Press, 1994, pp. 59-65; Peter Harrison,
"Curiosity, Forbidden Knowledge, and the Reformation of Natural Philosophy in Early Modern
England," Isis, 92 (2001) 265-290; Lorraine Daston, "Curiosity in Early Modern Science," Word
and Image, 1995, 11: 391-404; Roger Shattuck, Forbidden Knowledge: From Prometheus to
Pornography, New York: St. Martin Press, 1996; Neil Kenny, The Uses of Curiosity in Early
Modern France and Germany, Oxford: Oxford University Press, 2004.
4
that gave such resonance to St. Jerome’s interpretation of St. Paul’s dictum? On
the other end of Ginzburg’s narrative: What brought the change about in the 16th
century? What enabled astronomers, such as Copernicus, Tycho Brahe, Kepler
and Galileo, to transgress these prohibitions and to suggest new celestial
knowledge?
***
In order to answer these
queries it is useful to begin with a
renowned sixteenth century image
of Icarus. It is Peter Bruegel’s
painting in the Musée Royale des
Beaux Arts in Brussels of a
“Landscape with a Falling Icarus”
of 1567(?).
The painting depicts a magnificent landscape - in the background, a bay with
galleys at twilight; while in the foreground, a peasant is ploughing his field, a
shepherd with his flock and dog is watching the cloudless sky, and a fisherman is
busy with his nets. To the right, there is a barely perceivable element that
constitutes the painting's main subject: It is neither the peasant and his plough nor
the old man's corpse on the left-hand side, but rather the two legs of Icarus falling
into the sea. The immediate source for deciphering this enigmatic painting is
Ovid’s description of the fall of Icarus in Metamorphoses Bk. VIII
5
“And someone while trying to catch a fish with a trembling rod,
or a shepherd leaning on his staff, or a ploughman on his shaft
saw them and was dumbfounded …
he flailed with bare arms, [and] vanished into the dark blue sea, the Icarian
Sea, called after him.”5
In Bruegel’s paintings all the protagonists are in place: the fisherman, the
shepherd and the ploughman are situated above the bay while Icarus sinks into the
deep. Yet there are a few discrepancies, the most conspicuous being that the varied
figures are either indifferent to the mythical event or fail to appear amazed and
bewildered. It is clear that Bruegel meant his painting to comment on the Ovidian
myth, but what exactly is the content of this comment? 6
Art historians searched for textual clues for deciphering the iconography of the
painting in several verses from the New Testament concerning the ploughman as a
5
Ovid, Metamorphoses v-viii, ed. And trans. D. E. Hill, Warminster: Aris and Philips Publishers,
1992, Bk. VIII:217-223, p 113.
6
P. Roberts-Jones, Bruegel. La Chute d’Icare (Friburg, 1974); Robert J. Clements, “Brueghel’s
Fall of Icarus: Eighteen Modern Literary Readings.” Studies in Iconography 7-8 (1981-2), 25367; Christopher Braider, Refiguring the Real: Picture and Modernity in Word and Image, 14001700 (Princeton, NJ: Princeton University Press, 1993), esp. pp. 71-99; also Ethan Matt Kavaler,
Peter Bruegel: Parables of Order and Enterprise, (Cambridge, Cambridge U.P., 1999), pp. 5777; Robert Baldwin, "Peasant Imagery and Bruegel's “Fall of Icarus”, Konsthistorisk Tidskrift,
LV, 3, 1986, 101-114.
6
symbol of honest labor towards salvation. As a key to Bruegel's intentions they
emphasized especially the following verses from Luke 9:62, “Jesus said to him: No
man putting his hand to the plough, and looking back, is fit for the kingdom of
God” or St. Paul’s assertion in I Cor. 9-10: “he that ploweth should plow with
hope”. Others have turned to a German proverb declaring that: “No plow stops for
the sake of a dying man”. Others still turned to the skeleton hidden behind the
bushes in front of the plough as a signifier for the admonition of vanity, such as
the anamorphic skull in Holbeins’ Ambassadors. While all these are obvious
markers for the interpretation of Bruegel's painting, still Icarus, as the main
character in Ovid’s version, is excluded from these readings, and is turned into a
subsidiary figure.
In order to capture Bruegel’s intention there is a need to examine one further
discrepancy between Ovid’s version of the myth of Icarus and Bruegel visual
depiction of it. In Ovid it is midday and the sun is in zenith. In Bruegel the sun is
setting, and in another version of this same painting the sun is rising. These
different positions of the sun turn the viewer's attention to the opening verses of
Ecclesiastes: “The sun also ariseth, and the sun goeth down, and hasteth to his place
where he arose.” Reading further makes it clear that Bruegel could have these
verses in mind as a condemnation of Icarus’ curiosity and search for fame and
novelty. Against the pagan celebration of the human tragic quest after immortal
fame inscribed in the names of geographical places, Ecclesiastes declaims:
7
“The eye is not satisfied with seeing, nor the ear filled with hearing... there is
no new thing under the sun… there is no remembrance of former things…"
[Ecclesiastes 1:5,8,11]
These pronouncements can be directed also against the figure of Icarus as the
embodiment of vain curiosity. The author of Ecclesiastes stresses throughout that:
“Better [is] the sight of the eyes than the going of the soul." [Ecclesiastes 6:9]
The meaning of Icarus’ curiosity becomes his attempt to follow the
wanderings of his desire after knowledge of things that are beyond the power of
human sight.7 The biblical author denies the human soul's desires for what is not
directly given. In such a manner, the moral dimension, aiming at quieting desires
and passions, has immediate epistemological implications. One should embrace
appearances that are immediately present before one's eyes and not inquire and
speculate about hidden meanings and causes. The association of pride and
intellectual curiosity and search after vain knowledge is already emphasized in
Psalms: “Lord, my heart is not haughty, nor my eyes lofty: neither do I exercise my
self in great matters, or in things too high for me.” [Psalms 131:1]
Later generations emphasized this epistemological warning against human
desire for knowledge and vain curiosity. In the Apocryphal treatise The Book of
Sirach, one is warned:
7
In Ovid's words "desertuitque ducem, caelique cupidine tractus altius egit iter" [emphasis
added] in Ovid, ibid. lines 224-25.
8
“Seek not (to understand) what is too wonderful for thee,
And search not out that which is hid from thee.
Meditate upon that, which thou must grasp,
And not occupied with that which is hid.
Have naught to do with that which is beyond thee,
For many are the conceits of the sons of men,
And evil imaginations lead astray."8
The sense of Icarus’ curiosity that Bruegel, following Ecclesiastes, denounces
is not, therefore, related to the investigation of the heavens specifically but with
human dissatisfaction with the immediately given. Icarus’ vanity was in his
attempt, guided by his imaginations and desires, to pry into things that are beyond
the horizon of one’s visual field. The threshold, however, is not necessarily between
high and low, but between what can be perceived directly and what is beyond
human sensory grasp.
This emphasis on the epistemological barrier that divides what is
immediately given and can be fully known and what is distant and beyond human
perception is succinctly formulated in Aristotle's De partibus animalium. Aristotle
sets the power of human vision as the limit of human knowledge. Certain things,
one is told, are too distant and alien for humans to know.
8
The Book of Sirach, 3, 21-25 , The Apocrypha and Pseudepigrapha of the Old Testament, ed. R.
H. Charles (Oxford), I, 324.
9
“Of things constituted by nature some are ungenerated, imperishable, and
eternal, while others are subject to generation and decay. The former are
excellent beyond compare and divine, but less accessible to knowledge.
The evidence that might throw light on them, and on the problems which
we long to solve respecting them, is furnished but scantily by sensation.”
These super-sensual and perfect objects stand in contrast to animal and plants,
"living as we do in their midst,” about which ample data is available. An example
for such distant and eternal entities is celestial bodies. Of these, although they give
so much pleasure in their excellence, one has only “scanty conceptions.” And still
humans are excited and curious of them “just as half glimpse of persons that we
love is more delightful than a leisurely view of other things, whatever their number
and dimensions.” Terrestrial things, because of their affinity and nearness, are
known with certitude “in their completeness.” Human knowledge of celestial
things is lofty, they are beyond one’s grasp, and are known only as far as “our
conjectures could reach.” 9
This epistemological dimension of Icarus' air travel is explicated in the
satires of Lucian of Samosata in the second century A.D. His critical attitude is not
9
Aristotle, De partibus animalium, (On the Parts of Animals), Bk. I: Ch. 5, 645a21-645b6 in The
Complete Works of Aristotle, ed. Jonathan Barnes, 2 vols, Bollingen Series LXXI.2, Princeton:
Princeton University Press, 1984, pp 1003-1004 (One can compare Aristotle's dichotomy with the
above Ecclesiastes' differentiation between "sight of the eyes" and the "going (conjectures) of the
soul").
10
limited to Icarus’ attempt to reach higher things. Lucian embraces Aristotle's
epistemological distinction between human knowledge of things close by and their
inadequate perception of distant heavenly phenomena. And in the vein of
Ecclesiastes and Jewish Hellenistic literature, he denounces the astronomers’
attempt to reach beyond the limits of their senses.
"Indeed, my friend, it will make you laugh to hear about the way they
bragged and worked wonders in their talk! Why, in the first place, they
stood on the ground and were not a bit better than the rest of us who walk
the earth; in fact, they were not even sharper sighted than their
neighbours, but some of them were actually purblind through age or
idleness. In spite of that, however, they claimed to discern the boundaries
of Heaven, they measured the sun, they visited the spheres beyond the
moon, and you would have thought they had fallen from the stars from
the way they told about their magnitudes and presumed to say just how
many cubits it is in distance from the sun to the moon, often, perhaps,
without even knowing how many furlongs it is from Megara to Athens.
And not only did they measure the height of the air and the depth of the
sea and the circumference of the earth, but by the description of circles
and the construction of triangles on squares and of multiple spheres they
actually measured out the cubic content of the Heavens. Moreover, was it
not silly and completely absurd that when they were talking about things
so uncertain they did not make a single assertion hypothetically but were
11
vehement in their insistence and gave the rest no chance to outdo them in
exaggeration? "10
Lucian’s problem is not so much with the height of the heaven or with its symbolic
relationship with the divine Godhead, or with social hierarchy, but with the simple
epistemological assumption that certainty of knowledge stands in inverse relation
to distance: the nearer an object is, the better one can come to know it. One should
be satisfied with the here and now not only morally but also epistemologically.
What ever is beyond immediate human grasp is senseless.
In his descent to the underworld in search of the supreme philosophical
truth about the good life, Lucian’s cynic protagonist receives the following answer
from Teresias the ancient Homeric prophet:
“The life of the common sort is best, and you will act more wisely if you
stop speculating about heavenly bodies and discussing final causes and
first causes, spit your scorn at those clever syllogisms, and counting all
that sort of thing nonsense, make it always your sole object to put the
present to good use and to hasten on your way, laughing a great deal and
taking nothing seriously.”11
The moral and the epistemological emphases on the “here and now” are
entwined together in Lucian’s “True Histories”, his most pointed disparagement of
10
Lucian, Icaromenippus, or the Sky-Man translated by A. M. Harmon, in Lucian, 8 vols.
Cambridge, Mass.: Harvard University Press, 1913, vol. II, 277-279.
11
Lucian, Menippus or the Descent into Hades, ibid. vol. IV, 107-109.
12
curiosity. This satirical exposition is composed of a set of fantastic voyages, taking
the story teller to the moon, into the bowels of a whale, and to a series of islands
constituting the imaginary regions of dreams and the after-life. This strange trip is
set in motion by idle curiosity to reach beyond the limits of what is possible to
know. Lucian identifies symbolically the transgression of these limits with sailing
beyond the Pillars of Hercules in quest of vain knowledge of the unknown.
“Once upon a time, setting out from the Pillars of Hercules and heading
for the western ocean with a fair wind, I went a-voyaging. The motive and
purpose of my journey lay in my intellectual activity and desire for
adventures, and in my wish to find what the end of the ocean was, and
who the people were who lived on the other side.” 12
Through these voyages, Lucian is setting the limits of what can be known
and of what is worth knowing! The quest for whatever lies beyond these limits will
produce nothing but ridiculous and worthless stories. This quest is so futile that
such life-wasting curiosity in search of the unobtainable receives its due
punishment only in the afterlife: “Sentence was given that for being inquisitive and
not staying at home we should be tried after death.”13 Staying at home means for
Lucian not investigating what is beyond one’s reach: neither forward in space – it
serves no rational purpose to venture crossing the Pillars of Hercules; nor into the
future – Lucian’s greatest lie, as one of the earliest commentators adds in the
12
Lucian, A True Story, ibid. vol. I, p. 253.
13
Ibid., p. 313
13
margin, was his promise to tell more stories in his future work; nor investigating
what is above – as the result is the grotesque voyage to the moon; nor what is
below us – into the belly of the whale who inhabits the depth of the ocean. Finally
any attempt to truly know the past is futile and will result in absurd answers, such
as Homer who discloses that he is actually a Babylonian.
Lucian is setting the horizon of any possible knowledge, identifying it with
the actual horizons of one’s visual grasp. Only what is immediate can be known,
and is worth knowing. A much similar echo of such sentiment is found in the 2nd
Century Jewish literature. At the opening of Bk. III of the treatise Hagiga dealing
with the nature of esoteric knowledge, the following admonition is asserted:
“Every one who tries to know the following four things, it was better for
him if he had never come into the world, viz.: What is above and what is
beneath, what is in front (i.e. what was before), and what is behind (i.e.
what will be after). “14
It is possible, now, to point to a common grain of critical attitude to curiosity
prevalent in late antiquity.15 It was not an outcome of a mistranslation and it was
not restricted to the knowledge of higher things. The culture of the early centuries
A.D. was highly susceptible to such interpretation of St. Paul’s indignation of “high
14
The Mishnah, “Hagiga” 2.1, in The Mishnah, trans. And introduction and notes by H. Danby,
(Oxford, 1933), 213.
15
See also P. G. Walsh, "The Rights and Wrongs of Curiosity (Plutarch to Augustine)," Greece
& Rome 2nd Ser., 35 (1988), 73-85.
14
heartedness” as an epistemological prohibition on seeking knowledge of the
beyond. Furthermore, this resentment of curiosity was not concerned only with
knowledge of higher things (such as astronomy) but in general with the quest after
knowledge of things that are beyond the reach of human senses. The origin of
these prohibitions and admonitions was not only in religious fear, but more so in a
real epistemological problem: in order for one to know, one has to come into as
direct contact with the objects of knowledge as possible. To know something is
actually to grasp it.16 Icarus' desire to truly know heavenly phenomena led him to
attempt to fly there in a vain and disastrous effort to perceive them closely and
directly.
***
How do such instructions and admonitions accommodate both Jewish as
well as Greek celebration of human intelligence, learning and desire for true
knowledge? How is knowledge possible, if all one can truly and fully know is in
the immediate field of perception? How can human striving after knowledge be
kept on the middle path ('medio' que 'ut limite curras, Icare,' ait 'moneo…'),
commended by Daedalos to Icarus?
A possible answer is found in one of the Talmudic stories following the
above Mishnaic admonition. The sages tell of the mystical experience of four who
16
Stanley Rosen, "Thought and Touch: A Note on Aristotle's De Anima,” in his The Quarrel
Between Philosophy and Poetry: Studies in Ancient Thought (New York and London: Routledge,
1988), pp.119-126.
15
entered an orchard “Ben Azai, Ben Zoma, Other, and Rabbi Akiva. Told them
Rabbi Akiva when you come upon stones of pure marble do not say water, water,
as it is said “he that telleth lies shall not tarry in my sight. “ Ben Azai cast a look
and died… Ben Zoma peeped and [was mentally] impaired… Other cut the
plantation [a heretic], Rabbi Akiva departed in peace.”17
Rabbi Akiva's advice is simple: in one’s progress towards knowledge of the
divine, the most important thing is not to get confused. In order to stand in God’s
sight one has to be careful in deciphering what is in front of one’s own eyes. The
symbolic signification of confusing marble for water is the demarcating line
between the artificial and the natural, or the dynamic and its static representation.
In any case the message is that at each stage of the mystical progression one is to
verify and check only what is in one’s immediate field of vision, and not to peep, or
steal a glance of what is not yet open to sensory grasp. In other words, curiosity is
again interpreted as an attempt to look beyond what is given, and is still a
dangerous temptation because it leads to erroneous perceptions and confusion
between the different domains of the divine realm.
Another way of progression towards knowledge is the Aristotelian method.
For all their difference these two ways of knowing share two similar principles:
knowledge is based on what is immediately given, and going beyond that
17
The Babylonian Talmud, "Hagigah" 14b. For a slightly different translation: The Babylonian
Talmud: Seder Mo'ed- Hagigah, translation, notes, glossary and indices under the editorship of
Rabbi Dr. I. Epstein, London: The Soncino Press, 1938, p. 91
16
inattentively leads to error; and confusing the different domains of knowledge is a
categorical mistake to be avoided at all costs.
One of the aims of Aristotelian scientific method is to define the limits of
human desire for knowledge, and to determine what is knowable and to what
extent it can be known. Any science, according to Aristotle, begins with direct sense
perceptions. In On Generation and Corruption and in the fourth book of Meteorology
Aristotle defines the object of natural philosophy as being the potentially
perceptible body, corpus potentia sensibile. These perceptions are mixed and an act
of analysis and division, differentiating the diverse aspects of the phenomena and
assigning each its proper characteristics is demanded. For each aspect of the
observed phenomena there exists a special scientific treatment: Consideration of
change are treated by the science of physics, considerations of shape are a
geometrical matter etc. Each and every science has its own principles of
demonstration, and scientific demonstrations must be from proper principles and
cannot pass from one subject to another. In the Posterior Analytics Aristotle asserts
that: “One cannot, therefore, prove anything by crossing from another genus
(metabasis eis allo genos) – e.g. something geometrical by arithmetic.”18
At the core of the Aristotelian scheme is a basic notion of order (cosmos),
where each thing in the world has one unique characteristic that defines it, and in
accordance a unique place in the universe (its natural place). Thus, each science has
18
Aristotle, Posterior Analytics, bk I, ch. 7, 75a38, in The Complete Works of Aristotle, p. 122.
17
its own unique principles in accordance with its subject matter, just as each sense
organ has its unique sensibilia.
This attitude led the Aristotelian tradition to an intricate discussion of the
nature of mathematical sciences, such as astronomy, music and optics. In these
cases physical phenomena of change and motions were not explained according to
the precepts of physics but through mathematical demonstrations. In a sense, these
sciences demanded one to pry beyond the immediate given and to mobilize a
causal account from a different field of knowledge. The question of what exactly
was the status of such demonstrations haunted commentators of Aristotle through
the Middle-Ages and the Renaissance, leading to such notions as scientia media, or
“mixed sciences”. Such disturbing notions became even more alarming in the
context of emerging scholasticism of the 12th and 13th centuries.19
19
For extensive discussions of this theme see: W. Roy Laird, “Robert Grosseteste on the
Intermediate Sciences,” in Traditio 43 (1987), 147-169, and his “Galileo and the Mixed
Sciences,” in Method and Order in Renaissance Philosophy of Nature: The Aristotle Commentary
Tradition (eds.) D. A. Di Liscia, E. Kessler, and Ch. Metheun, 1997 253-270. See also: Carlos A.
Ribeiro do Nascimento, “Le Statut epistemologique de ‘sciences intermédiaires’ selon s. Thomas
d’Aquin,” in cahiers d’Etudes Medievales,2 (1974), 33-95; R. D. McKirahan, Jr., “Aristotle’s
Subordinate Sciences,” in British Journal for the History of Science 11 (1978), 197-220; S. J.
Livesey, “Metabasis: The Interrelationship of the Sciences in Antiquity and the Middle Ages,”
PhD thesis, Univ. California at Los Angeles 1982; idem, “The Oxford Calculatores,
Quantification of Qualities, and Aristotle’s Prohibition of metabasis,” in Vivarium 24 (1986), 5069; idem, Theology and Science in the Fourteenth Century: Three Questions on the Unity and
18
Early Scholasticism merged together the two strands of finding one’s way
through the woods of religious revelation and the logical order of the sciences. A
good example of such an effort is Hugh of St. Victor’s Didascalicon. In discussing
the right method for studying the Scripture, Hugh presents the following parable:
“Consider two men both travelling through a wood, one of them struggling
around in bypaths but the other picking the short cuts of a direct route: they
move along their ways with the same amount of motion, but they do not reach
the goal at the same time. But what shall I call Scripture if not a wood? It
thoughts, like so many sweetest fruits, we pick as we read and chew as we
consider them. Therefore, whoever does not keep to an order and a method in
the reading of so great a collection of books wander as it were into the very
thick of the forest and loses the path of the direst knowledge.” 20
In the Talmudic story the question of method is but alluded to, Hugh is explicit
that in order not to go astray in the great forest of religious mysteries caution is a
necessary principle of conduct:
“Two things are necessary, namely work and method for that work… He who
works along without discretion works, it is true, but he does not make
Subalteration of the Sciences from John of Reading’s Commentary on the Sentences (Studien und
Texte zur Geistesgeschichte des Mittelalters 25), Leiden, 1989.
20
Hugh of St. Victor, The Didascalicon of Hugh of St. Victor: Medieval Guide to the Arts, trans.
With introduction and notes by Jerome Taylor (New York and London: Columbia University
Press, 1961) 126-7
19
progress, and just as if he were beating the air, he pour out his strength upon
wind. “21
The method is the logical Aristotelian separation between the different disciplines
and ways of inquiry. The beginning of all learning is in this act of division and of
mapping the right path for one’s intellectual endeavor:
“But although all the arts tend toward the single end of philosophy, they do
not all take the same road, but have each of them their own proper businesses
by which they are distinguished from one another. “ 22
Such acts of separation and clear perception of what is before one eye’s is a
safeguard against getting lost:
“Seek, therefore, in every art what stands establish as belonging specifically to
it… Do not strike into a lot of by-ways until you know the main roads: you
will go along securely when you are not under the fear of going astray.”23
Those who do not follow the precepts of Hugh’s method are the impudent curious
who seek hidden things that can be revealed only as a final meditation not before.
“There are still others who … wish to search into hidden matters and to hear
about un-heard of things… their will is not evil, only senseless. “24
21
ibid.
22
ibid. 71.
23
ibid. 90.
24
ibid. 134.
20
This search after the curious facts leads the mind in a disorderly way to collect
different materials that lead to haughtiness and confusion:
“Certain persons, while they omit nothing which ought to be read,
nonetheless do not know how to give each art what belongs to it… It is not the
teaching of others that they accomplish in this way, but the showing off of
their own knowledge … Only consider how perverse this practice is. Surely
the more you collect superfluous details the less you are able to grasp or to
retain useful matters. ” 25
Such curiosity was equated to impudence:
“Impudence arises when we do not keep to the suitable order and method
of the things we are learning.”26
The right order begins with separation borders. Only then can the path to hidden
things be disclosed with no confusion:
“The method of expounding a text consists of analysis… We analyse through
separation into parts when we distinguish from one another things which are
mingled together. [Then] [w]e analyse by examination when we open up
things which are hidden.” 27
25
ibid. 89.
26
ibid. 127.
27
ibid. 150.
21
These strictures and warnings are not concerned solely with confusion and
ambiguity but with the anxiety of glancing at something that is not yet in full view.
Successful meditation of hidden mysteries takes place only at the end of the
learning process. Any other attempt to traverse beyond the actual scenery exposed
at each stage of student progression can be disastrous. The curious, in search of
hidden things, collects facts haphazardly that cannot be integrated into an
intelligible picture. This was intimately connected with the specifically medieval art
of memory as a mode of thinking and composing.
“In terms of mnemotechnic, curiosity constitutes both image “crowding” – a
mnemotechnical vice, because crowding images together blurs them, blocks
them, and thus dissipates their effectiveness for orienting and cueing – and
randomness, or making backgrounds that have no pattern in them.”28
***
These anxieties gave rise to a vast literature on the classification of
knowledge, in an attempt to secure the proper order of progress toward
knowledge, and what can be learned and viewed at each of the specified stages.
These medieval treatises combined didactic devices together with metaphysical
concerns that shaped the way different sciences were practiced. A case at hand is
Scholastic treatment of optics and vision. The first exponents of the new Arabic
optics in the West were attracted to the manner in which it combined mathematics
28
Mary Carruthers, The Craft of Thought: Meditation, Rhetoric, and the Making of Images, 400-
1200, Cambridge: Cambridge University Press, 1998, p. 82
22
and physics. Together with the Biblical status of light as the firstly created entity, it
enabled thinkers such as Robert Grosseteste and Roger Bacon in the 13th century to
install it as a corner stone for their theological speculations. This unique
amalgamation traversed the border-lines between the disciplines set in such
treatises as Hugh of St. Victor’s Didascalicon, in a way that seemed to allow real
opportunity for a theological revival leading to new revelations and salvation.
Roger Bacon asserted, in his discussion of the utility of the mathematical sciences
for divine matters, that geometry can serve as a mighty tool in explicating the
spiritual meaning of the Scripture. In order to decipher such mysteries as Noah’s
Ark, the Temple of Solomon and Ezekiel or Aaron’s vestments, one has to be "well
acquainted with the books of the Elements of Euclid and Theodosius and Milleius
and of the other geometricians.” Deciphering these geometrical secrets will
transform human sense of sight and will lead to the deepest mysteries contained in
the Scripture.
“Oh, how the ineffable beauty of the divine wisdom would shine and infinite
benefit would overflow, if these matters relating to geometry, which are
contained in Scriptures, should be placed before our eyes in their physical
forms! For thus the evil of the world would be destroyed by a deluge of
grace.”
Understanding the geometrical principles underlying such biblical constructions
would lead to a new visibility where the exposed mysteries would reveal
23
themselves not as allegorical and in spiritual form but would materialize in front of
the human contemplator.
“And with Ezekiel in the spirit of exultation we should sensibly behold what
he perceived only spiritually, so that at length after the restoration of the New
Jerusalem we should enter a larger house decorated with fuller glory. Surely
the mere vision perceptible to our senses would be beautiful, but more
beautiful since we should see in our presence the form of our truth, but most
beautiful since aroused by the visible instruments we should rejoice in
contemplating the spiritual and literal meaning of Scripture …which the
bodies themselves sensible to our eyes exhibit. Therefore I count nothing more
fitting for a man diligent in the study of God’s wisdom than the exhibition of
geometrical forms of this kind before his eyes.”29
This radical program aimed at instilling geometry into corporeal nature as well
as into the literal meaning of Scripture. Bacon hoped that this would lead to a direct
and immediate visual perception of the spiritual significance that lay concealed
beyond human post-lapsarian sensual grasp.
Such a program threatened the meticulous structure of scholastic progression
toward knowledge and was rebuked both on philosophical grounds and also
because of its transgression of the set borders of the disciplines. Bacon’s views
29
Roger Bacon, The Opus Majus of Roger Bacon, edited with introduction and analytical table by
John Henry Bridges (Oxford: 1897) Vol. 1, pp. 210-11, trans. Robert B. Burke (Russel and Russel
Inc., New York: 1962) vol. 1, pp. 223-234
24
were condemned in 1278 and he was put under arrest. In 1280 John Pecham has
undertaken to correct and re-arrange the science of optics in order to prevent any
future transgressions and confusions.
In the preface of his treatise Perspectiva Communis Pecham is well aware that in
the science of optics "glory is found physically as well as mathematically so that
perspective is adorned by the flowers of both." Yet this glory had its own dangers
and Pecham is set to re-establish the border-lines separating mathematics and
physics, lines that were obscured in former treatises on the subject:
“I shall compress into concise summaries the teachings of perspective, which
[in existing treatises] are presented with great obscurity.”
This is mainly concern with the differentiation between mathematical and
physical demonstrations “according to the type of subject matter”. It is especially
important to put the subject of light and vision into order as exactly at this
transitional area one is lured to peep beyond what is directly given: “As the Master
– the light – of all men deems the investigator of light worthy of illumination.” 30
Pecham structures his treatise exactly in response to this challenge. Each
traditional topic of the theory of vision receives its appropriate modicum of
mathematics. In some cases Pecham rejects the mathematical explanation as
unsuitable. In the case of radiation of light through pinholes, for instance, Pecham
30
John Pecham, John Pecham and the Science of Optics – Perspectiva communis, edited with an
introduction, English translation, and critical noted by David C. Lindberg (Madison: The
University of Wisconsin Press, 1970) p. 61.
25
rejects the mathematical explanation (“cannot serve as the whole cause”), and
prefers a physical explanation concerned with the nature of light (“light is naturally
moved towards this shape”).31
Pecham, by rearranging the propositions of optics, neutralized the radical
implications suggested by Bacon, and re-establishes that one can see clearly only
what in front of one’s face and only at an appropriate distance.32
***
The waning of the scholastic system and of the medieval universities,
together perhaps with the new voyages of discovery that left behind the Pillars of
Hercules brought the anxiety of “metaphysical voyeurism”33 back to the surface of
the European intellectual culture. Questions of knowledge and demonstration were
discussed in different social and cultural spheres of activity. Debates concerning the
scientific method took place all through European centers of learning from Padua
through the Lutheran universities of Germany to Paris and Oxford. A common
thread running through all these discussions and treatises was an attempt to
defend these threatened disciplinary boundaries for fear of confusion.
“Parmenides and Melissus committed similar errors, transferring to physics
not physical reasons but mathematical ones, confusing therefore the limits of
31
32
33
Ibid. Proposition 5, pp. 70-71.
For instance ibid. propositions 48, 49, 63 pp. 130-131; 140-141.
This expression from Walter Stephens, Demon Lovers: Witchcraft, Sex, and the Crisis of Belief
(Chicago: The University of Chicago Press, 2002) p.32.
26
the disciplines … one should diligently observe not to confuse the limits and
terms of the sciences; this is plainly the first step in any method.”34
Together with these admonitions the sixteenth century witnessed the revival of
the mythical figure of Icarus and of the lessons derived from his fall. The trouble
with Icarus’ curiosity, from the vantage point of sixteenth century scholars, was not
only in his endeavor to reach out to a forbidden sphere of knowledge, but in his
futile and absurd attempt to see and know things that are completely beyond the
grasp of human senses and reason. This renewed interest in Icarus was linked up
with a revival of the Lucian–style mocking of astronomers. These derisions aimed
not at astronomers’ attempt to know what is above, but at their presumptuousness
to inquire what is beyond the range of human perception. And thus Erasmus
repeats Lucian's ridicule:
"Theirs is certainly a pleasant form of madness, which sets them building
countless universes and measuring the sun the moon, stars and planets by rule
of a thumb or a bit of string, and producing reasons for thunderbolts, winds,
eclipses and other inexplicable phenomena. They never pause for a moment,
as if they'd access to the secrets of Nature, architect of the universe, or had
34
Jacob Schegk, De demonstratione libri xv. Nuvum opus: Galeni librorum eiusdem argumenti,
iacturam resarciens antehoc non visum, sed nunc primum in lucem, (Basle, 1564), fol. 147
Quoted in Sachiko Kusukawa, "Lutherans Uses of Aristotle: a comparison between Jacob Schegk
and Philip Melanchton", in Philosophy in the sixteenth and seventeenth centuries: conversations
with Aristotle, co-edited with Constance Blackwell, Aldershot: Ashgate, 1999. p.177
27
come to us straight from the council of gods. Meanwhile Nature has a fine
laugh at them and their conjectures, for their total lack of certainty is obvious
enough from the endless contention amongst themselves on every single
point."35
This was not only the aversion of a humanist scholar to the mathematical
practitioners, but it was an epistemological frustration that troubled astronomers
themselves in the sixteenth century. Icarus signified for sixteenth century
astronomers an acute awareness of the limits of their knowledge:
"God the Creator placed these bodies so far away from our senses that we are
unable to produce principles of demonstration for them (as we can in the
sciences of other things) or to discover what is natural and familiar, by means
of which we may afterwards set out the causes of particular appearances." 36
This is not a politico-religious prohibition but a technical discussion of the
possibility of visually experiencing heavenly events as physical events and not only
as mere appearances. According to the basic percepts of Euclidean optics the
35
Desiderius Erasmus, The Praise of Folly, trans., B. Radice (London, 1971), 151.
36
Frischlin, Nicodemus. 1586. De astronomicae artis, cum doctrina coelesti, et naturali
philosophia, congruentia. . . . Frankfurt: Spies.p. 41, quoted in Jardine, Nicholas. 1988.
"Epistemology of the Sciences." Pp. 685-711 in The Cambridge History of Renaissance
Philosophy, eds. by C. B. Schmitt, et al. Cambridge: Cambridge University Press, p. 700. See
also Peter Barker and Bernard Goldstein, "Realism and Instrumentalism in Sixteenth Century
Astronomy: A Reappraisal" Perspectives on Science 6.3 (1998) 232-258.
28
distance at which an object is seen is inversely proportionate to the size of the angle
of vision and beyond a given distance it is no longer visible on account of the
decrease in the size of the angle.37 Theological discussions of the power of sight
emphasized that only in the afterlife the Blessed can enjoy a perfect vision:
“The Blessed have keener eyesight, so they will see a thing under an angle
however small, and thus, however small a thing is and however far away it is
placed, they will see it. Hence there will remain no imperfection in them as
there is in us.”38
Thus even the great observational astronomer Tycho Brahe had to admit this
drawback. In his debate with Hartman over the question of the heavenly matter he
acknowledged that in the final account as a physical problem the matter of the
heavens was inscrutable (imperscrutabilis).39
It is in this context that the significance of the figure of Icarus in the sixteenth
century (both in the literature of emblems and in Bruegel’s picture) is divulged.
This was not only an expression of anxiety from transgressing into illicit domains,
37
Euclide, L’Optique et la catoptrique, French trans. By Paul Ver Eecke (Paris, 1959),
propositions III and V, pp. 3-4.
38
Alphonso de Tostado de Rivera Madrigal (1401-54/55), “Commentaria in IV. Part. Matthaei,”
cap. XVII, qu. CXVI, in Opera Omnia, edn (Cologne, 1613), vol.X, p. 414.
39
Tycho Brahe, Epistolarum astronomicarum libri (Uraniburg, 1596), p. 111, in Tycho Brahe
Opera Omnia, ed. J. L. E. Dreyer, 15 vols. (Copenhagen, 1913-29), reprinted, Amsterdam, 1972,
vol. VI, p. 140.
29
but also a frustration in the face of the shortcomings of human ability to know. In
the repeated warnings and admonitions of Icarus, one can sense that, to paraphrase
Hamlet’s mother: “They did protest too much, me thinks.”
A careful examination of Bruegel’s painting will noticeably reveal this
ambiguity; the general message of the image is the realization that “there is no new
thing under the sun… there is no remembrance of former things…” Yet, the
painting itself repeats the myth of Icarus and contributes to the perpetuation of his
fame. A further element is the sailing ships with their blown sails: Are they
returning safely to the harbor, or are they sailing out to the open sea, westward
towards the setting sun, aiming to cross the Pillars of Hercules for the new world,
like a similar boat a few decades later on the frontispiece of Francis Bacon’s
Instauratio magna? One witnesses in the falling of Icarus the clash between two sets
of values: the pagan notion of Fame and the Judeo-Christian quietism, the innate
limits on human capacity to know, and the human urge to break through these
barriers.
The same tension underlies other depictions of Icarus of the sixteenth
century and especially those Ginzburg put forward from the literature of emblems.
The apparent and straightforward expression of warning and indignation of those
“which paste theire reache doe mounte, whoe seeke the thinges, to mortall men
30
deny’de,”40 is presented entwined with the emblem’s aspiration to disclose hidden
meanings. The literature of emblems was a bold attempt to create new devices of
knowledge, through paradoxical games that conflated together different levels of
interpretation with different systems of sensory experience. By combining a verbal
expression, a puzzle and a picture, the emblem enabled the reader to bridge gaps
and inconsistencies in the different textual traditions, to look beyond language and
to conjure up the invisible secrets of nature. It combined in one picture the
transmission of knowledge, the explanation of its hidden meaning, together with
the potency of the image to create magical effects in the physical world as well as in
the human psyche. The emblem produced this effect by suggesting initially, a
fictive, yet rigid, spatial arrangement, within which a dramatic and fantastic action
took place. It further emphasized its paradoxical appearance by combining visible
signs with verbal puzzles, thus displaying different and only artificially connected
sensory systems.
Michael Maier characterizes his alchemical
treatise of emblems, Atalanta fugiens of 1617
as:
40
Whitney, Geffrey. A Choice of Emblemes, and other devises, For the moste part gathered out
of sundrie writers, Englished and Moralized. And divers newly devised. / by Geffrey Whitney.
Imprinted at Leyden, In the house of Christopher Plantyn, by Francis Raphelengius, 1586, p. 28.
31
"Partly adapted to the eyes and the intellect, with copper-etchings, and added
sentences, Epigrams and notes, partly [adapted] to the ears and to the
recreation of the soul with less than 50 musical fugues in three voices ... to be
seen, read, meditated, understood, judged, sung and listened with particular
pleasure."41
Maier's intention is the paradoxical combination of solitary contemplation and
sensual pleasure. The emblem makes it possible for the contemplative spectator to
awaken his mnemonic powers, not in order to induce fantasies of the sensual and
material realm but to rise into that garden where “roses of philosophy bloom”.
The alchemical emblems tackled the gap between the realm of concrete visual signs
and the hidden realm of universal concepts by turning this gap into a paradox, into
a serious play.42 In this play the “serious conclusions” are always ephemeral,
always hinting that things are not what they seem, and that any serious truth
41
Michael Maier, Atalanta Fugiens, hoc est, Emblemata nova de secretis naturae chymica
(Oppenheim, 1617).
42
On “Serious Jokes” and their role in late sixteenth century and early seventeenth century
intellectual world see: R.Colie, Paradoxia Epidemica: The Renaissance Tradition of Paradox
(Princeton NJ, 1966), Findlen, Paula. "Jokes of Nature and Jokes of Knowledge: The Playfulness
of Scientific Discourse in Early Modern Europe," Renaissance Quarterly 43 (1990), 292-331, and
Thomas DaCosta Kaufmann, "Arcimboldo's Serious Jokes: "Mysterious but Long Meaning," The
Verbal and the Visual: Essays in Honor of William S. Heckscher, eds. K. L. Selig and E. Sears,
(New York,1990) 59-80.
32
arrived at, will evaporate immediately in front of the frustrated gaze of the sinful
human mind. The emblems distort reality and force the human mind to turn its
gaze inside in search of a profound and invisible truth.
Francois Beroalde de Verville in his alchemical novel of 1610, Le Voyage des Princes
Fortunez summarized this practice as:
"The art of representing plainly that which is easily conceived but, which
under the coarsened features of its appearance, hides subjects quite other than
that which seems to be represented; this is practiced in painting when some
landscape or harbour scene or portrait is shown which conceals within itself
some other figure which can be discerned by looking from a certain viewpoint
determined by the artist. This is done also in writing, when an author
discourses at large on plausible subjects that unfold some other Excellencies
which are known only when read from a secret angle which uncovers
splendours concealed from common appearance."43
Within these visual images lay an urge to approach the invisible truth. These visual
tricks were machinated in order to let the spectator glimpse beyond the
epistemological barrier at the invisible realm “concealed from common
appearances”. It was a matter of a technical apparatus and solution to a crucial
epistemological problem, not only an act of transgression.
43
Translated in Stanislas Klossowski de Rola, The Golden Game: Alchemical Engravings from
the Seventeenth Century (London: Thames and Hudson, 1988), p. 28.
33
The same technical barrier allowed astronomers to deal only with distant
and blurred appearances and not with physical phenomena and causes. On the
close of the sixteenth century this became a source of both epistemological anxiety
and a technical concern. Various philosophers and astronomers (Jacopo Zabarella,
Lodovico Carbone, Ursus to name but a few) argued that astronomy had but a
limited claim for knowledge, and that it was based on mere fictitious hypotheses.
Tycho Brahe’s plan to reform astronomy and bypass these difficulties with better
contraptions and instruments of observation stumbled over sundry problems of
measurements and analyses of observed celestial phenomena (his polemics with
Hartman over the refractions of stellar light, the changing size of lunar diameter
during solar eclipses, and his bitter confrontation with Ursus).
The failure of Icarus to reach the heavens designates the common
denominator of the methodological discussions over astronomy towards the end of
the sixteenth century: Since one cannot reach the heavens, one cannot perceive
heavenly phenomena directly. Therefore, astronomy is condemned to treat
apparent motions only and is unable to investigate hidden causes, but to confine
itself in suggesting possible and reasonable causal hypotheses.44 Just a few years
later the Imperial mathematician and famous astronomer Johannes Kepler
44
For instance see: M. Maestlin, De astronomiae principalibus et primis fundamentis disputatio
(Heidelberg, 1582), folA2v: "Astronomia… enim est scientia, quae motus corporum coelestium
scrutatur et explicat… Apparentia enim motuum non physicis, sed mathematicis rationibus
demonstrantur."
34
commented on Alciati's emblem of the falling Icarus that: “no one falls, laying flatly
on the earth.”45 With these words Kepler hinted that astronomical knowledge can
be attained without flying into the heavens, and without directly perceiving
heavenly phenomena. What has allowed Kepler to suggest this change in
astronomical knowledge? How can true knowledge (and for Kepler this meant
causal knowledge) evolve without direct and immediate contact with its objects?
***
In 1604, an increasing sense of crisis led Kepler to the conclusion that a new
optics is needed in order “to uphold astronomy’s dignity and to subdue the hostile
fortress of doubt.”46 The task was to find a new view point and “a secret angle”
from which celestial phenomena could be measured and be physically known.
With this mission in mind, he published his optical treatise Ad Vitellionem
paralipomena, quibus astronomiae pas optica traditur.47 Examining this couplet
"Astronomiae pars optica" against the backdrop of classical and medieval philosophy
45
Kepler's complete comment reads "Nemo cadit, recubans, terrae de cespite planae; Ocuras
hominum, o quanta est in rebus inane." (Francisco Sanchez of Salamanca, Commentary on
Alciati's Emblemata, Lyons 1573, in the British Library, Egerton MS 1234).
46
Johannes Kepler, Ad Vitellionem paralipomena, quibus astronomiae pars optica traditor
(Francofurti, 1604) published in Johannes Kepler, Gesammelte Werke, eds. Walter von Dyck and
Max Caspar, 24 vols. (Munich, 1937-), vol. 2, ed. Franz Hammer, p.6 [my translation].
47
Unless otherwise is stated I have used the following English translation: Johannes Kepler,
Optics: Paralipomena to Witelo and Optical Part of Astronomy, translated by William H.
Donahue, Santa Fe, New Mexico: Green Lion Press, 2000.
35
discloses a surprising oxymoron: can there be optics, that is, an account of visual
experience, of the heavens? Since classical theories of visual perception, as noted
above, accentuated direct contact with the perceived object, the remoteness of the
stars leaves the observer with only indirect and uncertain appearances. The
heavenly visual signs are only hints to a reality one cannot perceive directly. All
that an astronomer has to fall back on are hypothetical conjectures. The outcome of
this classical epistemological position was a divorce between observation and the
actuality of the heavens.
Kepler's new optics intended to do just this, to allow observation of distant,
and almost invisible, objects to grant knowledge as valid as the observation of
things at hand. Such new optics would allow measurement of invisible lines and
circles and yet these measurements would substantiate physical truths far more
certain than the measurements of static solid and corporeal objects. Paradoxically,
Keplerian optics would prefer indirect visual experience of shadows and virtual
images over direct experience of tangible entities. What is the mechanism that
allows such apparently absurd optics to work? What are the epistemological
foundations of such a scientific oxymoron: optics - or a science of visual experience
- of things that are beyond the power of one's eyesight?
At the opening sentences of his optics Kepler presents geometry and
mathematics as the tools that would allow astronomers to observe the heavens as if
directly.
36
“Astronomy… fl[ies] up into heavens, supported … by (as it were) a pair of
wings, geometry and arithmetic.” 48
These mathematical disciplines would serve like the wings of Icarus to lift the
human observer to the sky. However, these wings would not melt and, unlike
Plato’s allegory of the winged soul, would allow the astronomer more than a mere
ephemeral glimpse at the celestial phenomena.
Kepler trusts that these new tools would transform astronomy into a
physical science. Through careful application of mathematics, astronomy would be
able to investigate not appearances but “the motions of the heavenly bodies”
themselves. The mission Kepler sets for his new science is to "direct the eyes to the
central mystery of the cosmic machine". 49The only way to achieve this task is by
reformulating the nature of visual experience in general and the nature of scientific
observation in particular. How can Kepler assess an optical theory that concerns
48
Kepler, Optics, p.13. The obvious allusion is to Plato's allegory of the winged soul in Phaedrus,
246. Closer in time is P. Melanchton, Praefatio in arithmeticen Joachimi Rhetici (1536): "Sunt
igitur alae mentis humanae, Arithmetica et Geometria. Has si alligaverit sibi aliquis praeditus
ingenio non sordido, facilime penetrabit in coelum ac libere in coelestium coetu vagabitur, et illa
luce ac sapientia fruetur." In Corpus Reformatorum, ed. C. G. Bretscneider, vols. 1-21 (18341860), vol. 11, 288. Quoted in Charlotte Metheun, Kepler's Tubingen: Stimulus to a Theological
Mathematics (Aldershot: Ashgate, 1998) p. 75. See also Nicholas Jardine, The Birth of History
and Philosophy of Science: Kepler's A Defence of Tycho against Ursus with Essays on Its
Provenance and Significance (Cambridge, Cambridge University Press, 1984), p. 186 n.168.
49
Kepler to Maestlin, 1/11 June 1598, GW vol. 13, p. 225.
37
itself with invisible elements? How does such optics supply the means to measure
an empty space?
To tackle such a task Kepler cannot content himself with reiterating traditional
optical theory; he has to redefine the tenets of optics in order for it to accomplish
these expectations. The main revision is ontological. At the core of medieval theory
of perspective lay the notion of species as a physical expression or communication of
the visible body itself. The multiplication of species was molded into a visual ray in
the case of sight and into physical radiation in other cases of action at a distance
(such as in the case of a magnet), light being just a paradigmatic case. Kepler’s
revolutionary alteration takes place almost unnoticed:
“The things optics considers in astronomy are either the things themselves set
before the sense of sight, where the species of things, that is light and shadow
are considered.” 50
The identification of species with light and shade radically undermines medieval
optics and theories of cognition. The objects of sight are no longer emanations of
physical things, that can guarantee the success of the cognitive process in keeping
direct contact with external reality, but merely light or its absence reflected back
from the visual field.
Kepler abandons visual rays and physical emanation and reduces them all to a
radiation of light. This discreet maneuver releases optical research from
50
Kepler, Ad Vitellionem, p. 15. [my translation]
38
psychological considerations of intentions and cognition, allowing Kepler to take
optics as a physical study of light. It allows him, further, to reduce these studies to
the questions of the transition of light through media:
“The medium, through which light the carrier of species travels, by the cause
of it, one way or another, light reaches us refracted.” 51
Besides light and its travel through different media, optics deals with the
instruments of observation and the eye as receptors of these refractions.
In this way Kepler reduces all visual experience to refractions of light, and therefore
there is no difference in observing the distant heavenly bodies or an object in the
immediate visual field. The images produced are, in the final account, effects of
refractions of light.
This becomes clear when Kepler moves on and narrows the general definition of
optics and discusses specifically the celestial bodies. Here he emphasizes that the
astronomer considers only the species of these bodies transmitted as light, and that
these species are nothing but their mathematical properties, namely figure and size.
Therefore in order to capture visual phenomena there’s no need for a complete
imagery, with all its sensual details of colors and texture. Since light transmits
quantifiable properties only, also mere shadow can now suffice as the foundation
for true analysis of physical phenomena. Kepler thus reduces the entire visual
world to a theatre of reflections and refractions of light, turning the absence of
51
Kepler, Ad Vitellionem, p. 15 [my translation]
39
material bodies into a foundation of true knowledge of creation. His intuition is
based on the role of eclipses (in other words the absence of the luminaries) in
instituting astronomical science.
“For the most noble and ancient part of astronomy is the eclipse of the sun and
the moon, a subject that, as Pliny says, is in the entire study of nature the most
wondrous, and most like a portent.”52
The disappearance of the luminaries is the basis of any inquiry and is the
invitation God left the human race to study His creation. This invitation is ordered
like a theatre with signs and allusions to be deciphered by the human mind which
is the likeness of God Himself:
Anyone who ponders this [the eclipsed luminaries] carefully will find … both
that there is God, founder of all nature, and that in the very mechanics of it he
had care for the humans that were to come. For this theatre of the world is so
ordered that there exist in it suitable signs by which the human minds,
likenesses of God, are not only invited to study the divine works… but also
are assisted in inquiring more deeply.
Emphasizing the theatrical metaphor, Kepler compared the eclipsed luminaries
to playful jests Nature performs to lure the human mind to contemplate the true
order of the world.
52
Kepler, Optics, p. 15.
40
This process is aptly described in the introductory epigrams to Ad Vitellionem.
One of the Epigrams presenting a dialogue between the eyes and the minds ends
with the latter guarantying to restore the damage suffered by the eyes on its behalf
and to radiate starry brilliance from the "stains" and defects.53 What is this "stain,"
radiant with knowledge and what is the knowledge Kepler hoped to gain from
such a defect? Kepler explicates these words in the preface:
"Now, one may consider, that all the rest of Astronomy is closely
associated with the motion of the Sun and the important assistance given us
by the Moon, participating in the days just as in the nights, when all other
means failed us: it is believed rightly that universal astronomy is born from
this obscurity of the luminaries. Just as these darknesses may be the eyes of
the astronomers, these defects may be a rich source for doctrines, and these
stains may illustrate the most precise pictures on the mortal mind. O most
excelled and commendable argument for all the nations about the glory of the
shadow." 54
53
Kepler, Ad Vitellionem, GW, vol.2:
Mens: Qua licet expediam; faueat modo fama loquenti;
Mortales chartis perpetuabo meis.
Hic etiam referam, quae pro me damna tulistis:
Hicque suum et naeuis irradiabo iubar.
54
Kepler, Ad Vitellionem, p.16 "Iam qui perpenderit, quam arcte tota reliqua Astronomia cum
Solis motu copuletur, quantumque nobis Luna, diei noctisque particeps, opitule'tur, quando nos
41
Kepler, in a surprising turn of phrase, turns the Platonic allegory of the cave on
its head. It is the shadows, the obscurity, and the material effects of light that
become the source of knowledge.55 The astronomer is not supposed to observe the
sun itself but to examine its shadow in order to portray the true picture of the
universe and to reveal its secrets. The quantification of shadows (i.e., the absence of
the material object) is the key to Nature's powers. In sharp contrast to both Platonist
and Aristotelian philosophy, Kepler asserts that a true investigation of the
shadows, one that will define them correctly, then measure and analyse them
accurately, will finally expose the true structure of the universe.
“And thus the quantity of the image which the moon or the sun, whether
whole or eclipsed, shows us, and of the shadow which the earth stretches out
to the moon, must be carefully investigated by the astronomer.”56
Kepler points to the difficulties involved in such a research:
omnia alia media deficiunt: iure credet, vniuersam Astronomiam his luminium obscurationibus
inniti, adeo ut hae tenebrae sint Astronomorum oculi, hi defectus doctrinae sint abudantia, hi naeui
mentes mortalium preciosissimis picturis illustrent. O eximium et omnibus gentibus commendabile
argumentum de Vmbrae laudibus." [my translation]
55
For the epistemological status of shadows in Kepler's science see: Raz Chen-Morris, "Shadows
of Instruction: Optics and Classical Authorities in Kepler's Somnium," Journal of the History of
Ideas 2005, 66: 223-243.
56
Kepler, Optics, 16
42
“Even though these images are obvious to everyone’s eyes, all practicing
astronomers complain that it is with difficulty that they are measured. This is
partly because the bodies have a very narrow apparent size, and partly
because they constrict the eye with their exceptional light, so as to prevent
their fulfilling their function in seeing.”57
It is here that Kepler introduces instruments of observation as a corrective to the
feeble human eyes. The prototype of such instruments is the camera obscura:
“Nature has not forsaken those desirous of learning, for she has shown us a
procedure by which we may accomplish in darkness, without detriment to the
eyes, what is completely impossible in clear light, with the eyesight directed
towards the sun.”58
Kepler constructs a new place for astronomical observation; instead of the
human eye as the natural and obvious instrument of sight, it is the camera obscura as
a theatre of light and shadows. Within this theatre the main characters in nature’s
play are eclipses or blemishes that baffle the human senses and intrigue the human
mind. In such a theatre the observer is able to artificially produce shadows and
stains of light as the exact representations of the heavenly bodies, and to measure
them. An important part of the optics will have to account for the possibility of
observation through artificial instruments as a substitution to the natural naked-eye
57
58
ibid.
ibid.
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gaze at the heavens: “For aside from this, no other sure procedure can be
established for measuring something that happens in the sky.”59
In reducing visual phenomena to light and shade, their measurable
dimensions and motions, Kepler is able to condense heavenly phenomena, and
literally to bring them down into his “dark chamber”. As light is the divine
messenger communicating all terrestrial and celestial occurrences60, there is no
need to fly to the sky or to come down from the stars in order to account for them.
Kepler's camera obscura supplied seventeenth century science with a paradigmatic
case of artificial observation, leading only a few years later to Galileo's telescope.
Building over this paradigm the new slogans of the new science with their
emphasis on sapere aude meant nothing else but the courage to apply the new
instruments of observation and to artificially re-produce the hidden secrets of
nature in the safety of the laboratory.
59
60
Kepler, Optics, p. 57
For instance ibid. pp.19-20: "[I]f I say, this principle… the chain linking the corporeal and
spiritual world, has passed over into the same laws by which the world was to be furnished. The
sun is accordingly a particular body, in it is this faculty of communicating itself to all things,
which we call light."
44