1. Some Remarks on the History of Optics
The intense study of optical phenomena found in the seventeenth century and afterwards had
its roots in Greek Antiquity with the elaboration of concurrent theories on the vision process
(Lindberg, 1976; Ronchi, 1970, 1991). Lindberg (1976) locates in Greek Antiquity the origin
of three approaches to optics that persisted in time and often overlapped. The physiological
and anatomical approaches that ultimately converged in the ophthalmology; the
philosophical, were ontological, epistemological and psychological questions founded theirs
first answers, and the mathematical approach oriented to the spatial perception.
Is at the crossroad of these traditions that rests the work of Johannes Kepler (15711630) (Darrigol, 2012; Lindberg, 1976). In fact, we found in Grant (2003) a clear exposition
of the transmission, circulation and appropriation processes of the ancient knowledge both by
Arabic scholars and in European medieval Universities that reinforces the continuity
interpretation.
Moreover, astronomical observation and problems related to the observational
instruments gave a new impetus to optical studies. If the pinhole camera, widely used in
astronomy already defied Kepler’s optical knowledge (Darrigol, 2012; Hon & Zik, 2009) the
appearance on the stage of the telescope brought the need of new insights. Interesting enough,
the astronomical utility of optical knowledge seems to add more continuity in the process of
the construction of optical knowledge.
The concept of ray of vision was introduced in optical theories in early stages of its
development by Euclid (fl. 300 b.C.) (Lindberg, 1976, pp. 11-15). He developed a purely
geometrical account of the vision process that provided the conceptual tools on which later
work on the subject elaborate: Geometry no more left the optical studies.
To Euclid, the ontological status of the ray of vision wasn’t a purely mathematical
concept but the “physical agents of sight” (Lindberg, idem). Ptolemy (c.90 – 168)
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accomplished to become the major influence in later optical studies with his Optics. The
“greatest optician of antiquity” as Lindberg (1976) named Ptolemy, postulated the
equivalence of the rays of light and rays of vision but addressed a different ontological status
to the rays of vision (or of light): they become a mathematical entity1. Moreover Ptolemy
adhered to the Aristotelian concept of colour. To him, “colours were inherent qualities of the
(surface of) the bodies activated by daylight and sensed by the visual pneuma” (Darrigol,
2012).
Arab scholars played a decisive role both in the preservation of knowledge of the
Ancients, as in improving it with new insights. In fact medieval scholars from the XII and
XIII draws on the work of them. This constitutes a beauty network of readings, translations,
commentaries that allow the preservation and continuation of optical science. Two scholars
must be addressed. Al-Kindi (c. 800-870) was an Arab scholar with important
accomplishments in Metaphysics, Phycology and Sciences. In optics, according to Adamson
(2011) he
followed the tradition inaugurated by Euclid, and carried on by Ptolemy and others, in
which geometrical constructions were used to explain phenomena such as visual
perspective, shadows, refraction, reflection, and burning mirrors. This procedure
implies that light and vision can be formalized as geometrical lines, an implication
that al-Kindi and his sources embrace by claiming that vision occurs when “rays”
emitted from the eyes along straight lines strike a visual object.
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As in other fields of knowledge the ancient Greeks provided a rich and elaborated accounts on the vision
process. The debate of whether there was a flux emanating from the eyes (Pythagoreans) or a flux, of a different
nature, coming from the objects to the eyes (Atomists) or yet some other combination (Plato, Empedocles and
others) was only resolved in the eleven century by the Arab scholar Ibn al-Haytham known in the Latin world as
Alhacen.
2
Alhazen (965-c. 1040) follows and improve on Al-Kindi’s work and both are credited with
the principle that light emanate from each point of an observed object in all directions.
(Galili, 2010; Langermann, 2007)
Kepler’s synthesis of prior optical knowledge with both new insights made by
perspectivists and anatomists as well the pressing problems put by images from pinhole
camera and telescopes gave rise to the modern account of the vision process2 . This
accomplishment was accompanied by a shift on the ontological status of the ray of light
which become a model for the propagation of light3. We note the precarious ontological
status of ray of light in the forthcoming years for Newton defined it as the least part of light
that maintains light proprieties (Newton, 1704, pp. 1-2).
Descartes in the Dioptrique and Meteores, published in 1637 in the Discourses
(Descartes, 1965) elaborated further on Kepler’s theory of the retinal image and on the
explanation of the rainbow and pave the way to Newton’s work on optics thirty years later
(Shapiro, 1984; Westfall, 1980, p. 161). Newton, although knowledgeable of Kepler’s theory
of vision in his early optical studies did not read Kepler but “acquired a firm command of
contemporary optics through his studies of the works of Boyle, Descartes, and Hooke”4
(Shapiro, 1984, p. 9)
2
See e.g. (Darrigol, 2012), (Lindberg, 1976), (Straker, 1981), (Westfall, 2003). A rich historiographical debate
on the role of Kepler’s work as a culmination point of the perspectivists tradition (e.g. Lindberg, 1976) or as a
rupture with previous scholars’ conceptions (e.g. Chen-Morris, 2001; Straker, 1981) permeates the historical
account of Kepler’s contribution. This kind of rupture-continuity debate can elicit some more philosophical
oriented topics. However, in this work, we will not enter into them.
3
See for example (Chen-Morris, 2013; Darrigol, 2012; Gal & Chen-Morris, 2010). Although Ptolemy already
saw light rays as a mathematical tool, scholars’ ontological beliefs varied much across the next centuries. See
e.g. (Dupré, 2012).Moreover the canons of rationality changed. It’s problematic to talk about science and
scientific reasoning using the same words and maintaining its meaning to work out the ideas of the Ancients, the
medieval scholars or the Renaissance perpectivists. Things turn out to become more blurred with the Scientific
Revolution. See Chen-Morris (2001, p. 456) and note 2 from p. 462. Also Dupré (2002) emphasise
appropriation instead of transmission between the antiquity and Middle Ages scholars and the sixteenth century
authors for the later “still read the optics of antiquity and the Middle Ages, but it read the same optical texts
differently and put them to other cognitive ends.”(p. 18).
Boyle’s Experiments and Considerations Touching Colours of 1664 were published when Newton was in his
last year as an undergraduate and exercised a major influence in his first optical studies. The same can be said
with Hooke’s Micrographia of 1665, “the most comprehensive treatment of colour yet given by a mechanical
philosopher (Shapiro, 1984, p. 9). From both works Newton drew some insights. Descartes’s Dioptrice,
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The “New theory of light and colours” (Newton, 1671) was presented to the Royal
Society as a letter to Oldenburg, secretary of the Royal Society, following the protocols of the
time. It appears in the Proceedings as a paper with less than thirteen pages and only one draw
of an experimental setup. Several critics sparked by the “New Theory” was caused by
misunderstanding of some of Newton’s arguments (Shapiro, 1996). Moreover Newton was
developing his own methodology in contrast to the hypothetical philosophy of Descartes and
Leibniz (Anstey, 2004; Shaffer, 1990).
We must not forget that the “New Theory” aimed to substitute the venerable
peripatetic theory that sunlight is the simplest and homogeneous light and colours arouse by
mixtures of white and black to one where the sunlight is composed of different refrangible
rays of light and colours are unambiguously linked to the different refrangibility of the rays.
The careless presentation while led to an important amount of scientific correspondence that
allow Newton to refine his own ideas and strengthen his arguments, delayed the appropriation
of the “New Theory” (Shapiro, 1996; Westfall, 1980).
The beginning of Newton’s work in optics was also linked to his academic duties as a
student and then as lecturer at Cambridge. In 1667 and 1668 Newton attended Isaac Barrow’s
lectures on optics. By early 1669 Newton proofread Barrow’s optical lectures, from which he
worked out to what became his own Optical Lectures. These early works were then
developed and assembled in 1790s to constitute a significant part of the Opticks. (Shapiro,
1984)
When the Opticks were published in 1704, the Newton’s theory of light and colour
was already taught in several universities of Scotland and England (Shapiro, 1996, pp. 9394). Although the theory was subjected to an appropriation and interpretation associating it
with a corpuscular model of light, the theory as exposed in his Opticks was model-
Meteores and Geometrie also exercised significant influence on Newton who read those texts by a Latin
translation of 1656. (Hall, 1955; Westfall, 1980, p. 156)
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independent (Cantor, 1983; Darrigol, 2012; Raftopoulos, Kalyfommatou, & Constantinou,
2005). In the thirteenth query to the first Opticks edition Newton indicated his openness to
consider light as a wave
Do not several sorts of rays make vibrations of several bignesses, which according to
their bignesses excite sensations of several Colours, much after the manner that the
vibrations of the Air, according to their several bignesses excite sensations of several
sounds? And particularly do not the most refrangible rays excite the shortest
vibrations for making a sensation of deep violet, the least refrangible the largest
[vibrations] for making a sensation of deep red (...) (p. 136)5
In later editions, namely in the Latin edition of 1706, which fulfil all learned European
philosophers not at ease with the English language, then comprised almost all French ones,
for instance, Newton added queries that make an explicit preference for light as comprised by
corpuscles (Cantor, 1983). However all statements related to the nature of light remain in the
form of queries. As Darrigol (2012) say, “many authors adopted the concept of light as a flux
of corpuscles emitted by a source, thus turning a Newtonian query into a certainty.”(p. 109)
The fast appropriation of Newton’s main achievements was associated with the rise of
experimental physics demonstrations, a philosophical practice in crescendo all over the
Europe by the early eighteenth century (Shapiro, 1996). A positive heuristic on how to
manipulate prisms in order to obtain ‘good’ results and a set of experimental settings to
demonstrate by experiments the propositions, paved the way to lecturers develop their work
in the framework of the already strong experimental philosophy movement. Moreover, the
almost ready-made of Opticks to teaching purposes – eight definitions and equal number of
Sabra (1963) settled down that Newton’s ‘bigness’ was intended to refer wave-length and not amplitude as
interpreted by Duhem and others.
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axioms, followed up by the propositions of the theory in the first Book speed up the process
of appropriation. Meanwhile Newton had published his Principia in 1687 and in 1703
became President of the Royal Society. For all this the Opticks of 1704 was meant to spread
all over Europe the “New Theory”.
Hooke refereed the Newton’s 1671/2 letter to the Royal Society but saw the “New
Theory” as presenting one hypothesis among others (Shapiro, 1996). In that same year of
1672 Hooke presented a letter to the Royal Society stating the two battlefields for the grand
debate that would take place: On the acceptance of the relation of unequal refrangibility with
colours as stated by Newton and on the nature of light itself.
By the time Hooke and Huygens worked out theirs theory of light, the mathematic of
waves wasn’t yet been developed6. Huygens considered not periodic pulses but wavelets.
This was a great handicap to provide what later become known as the wavelike theory of
light, with the same persuasive power of Newton’s. Moreover Huygens had not provided a
treatment of colours in his Treatise of light composed before 1678 and published in 1690. He
stated in the Preface that he doesn’t attack the phenomena of colours “in which no one until
now can boast of having succeeded” (Huygens, 1912, p. vii), in a reference to Newton.
Interesting enough is to see how Huygens in the preface to the Traité unveil in
several passages the weaknesses of his theory in contrast to the young Newton’s bold
presentation of the “New Theory”. In fact, stating that “There will be seen in it
demonstrations of those kinds which do not produce as great a certitude as those of
Geometry” (idem, p. vi) would eventually not be so reassuring as Newton’s claims. Or in the
assertion that “I hope also that there will be some who by following these beginnings will
penetrate much further into this question than I have been able to do, since the subject must
Huygens’ geometric construction, allowed him to explain the double refraction of light in Iceland crystal. This
was a main achievement in optical theory of the time. Moreover the Iceland crystal seems to have developed an
instrumental role in persuading Huygens to develop his optical theory. In Dijksterhuis (2012) we found an
interesting account on this as well on the role and work of Rømer and the determination of the finite velocity of
light. Also (Darrigol, 2012, pp. 64-71) gave a very informative account of Huygens construction.
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be far from being exhausted.” (Emphasis added) (Idem, p. vii) The Huygens’ methodology
also differ from that of Newton’s for as stated by (Huygens, 1912):
There will be seen in it demonstrations of those kinds which do not produce as great
a certitude as those of Geometry, and which even differ much therefrom, since
whereas the Geometers prove their Propositions by fixed and incontestable
Principles, here the Principles are verified by the conclusions to be drawn from them;
the nature of these things not allowing of this being done otherwise. (p. vi)
In fact Huygens was much closer of the mechanistic philosophy of Descartes while Newton
was already sustaining his investigation on new foundations7. (Shapiro, 1989, pp. 225,226)
2.1 Diffusion and assimilation of Newton’s theory
Seventeenth century began with Galileo observations with the telescope in late 1609
and early 1610. In this same year Kepler wrote his Dioptrice, explaining why Galileo saw
what he saw, that is, why that particular setup of the lens allows the natural philosophers to
draw inferences upon Nature. The use of that instrument in natural philosophy pressed the
natural philosophers to build better telescopes and work on better optical theories.
By the end of the century Newton was ending up his Opticks and the theory was being
assimilated and worked by a growing number of scholars. Between 1671/2 and 1704 the
“New theory of light and colours” and the discussions it triggered had managed to clear some
conceptual difficulties. Huygens and his supporters could not be able to offer a working
7
Several natural philosophers beyond the few already mentioned developed an important role in establishing the
optical knowledge of the seventeenth century. To a scholarly account of the process we address expressly to
some of the literature already mentioned: (Darrigol, 2012), (Shapiro, 1989, 1996, 2008), (Schaffer, 1989). We
are also in debt to some works on this same theme: (C. C. Silva & Moura, 2012), (Andreou & Raftopoulos,
2010).
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theory. However this was not an obstacle to several natural philosophers thought about light
as a vibration. In fact both Darrigol (2012) and Cantor (1983) consider classes of theories
(Darrigol named it categories) as a heuristic device to develop their narratives. For, as Cantor
(1990) said “theories about the nature of light need to be read in relation to a scientist’s other
commitments, both in other branches of science and in philosophy and theology.” (p. 628)
Guerlac (1981) 8 give an account of the “New Theory” reception in France. At that
time English was not a language much read among learned French philosophers and
mathematicians and a Latin translation appeared in 1706 that allow a faster spread of the
Opticks content. In Germany, Leibniz, had been aware of Newton’s work since it was
delivered to Royal Society in 1671/2 and in 1704 read the Opticks. According to Shapiro
(1996), Leibniz expected that Mariotte´s experiment in France would come to confirm the
Newton’s theory and not to refute it9.
All over the Europe, Universities and colleges in the eighteenth century adopted
experimental demonstrations in classes of natural philosophy. Newton’s Opticks with its
queries open to interpretations, offers a good first raw material to a fast appropriation by
different traditions. But that should be worked out in different traditions in order to be
appropriated.
Cantor (1983) underline the pedagogical role of experimental demonstration and the
necessarily simplified theory presented to English society in the first four decades of the
eighteenth century. As he says, most learned Newtonians engage in the process of
Darrigol (2012, pp. 121-136) offers a very interesting account of the appropriation of Newton’s optics in the
eighteenth century in Britain and in the European continent. He emphasizes the influence of the Dutch, “the
earliest and most read Newtonians” (p. 123).
9
In fact Schaffer (1989) gave a different and in part conflicting account with Shapiro’s narrative on the
assimilation of Newton’s theory. In particular with respect to the Leibniz expectation on the outcome of
Mariotte’s experiment. These differences are due mainly on the emphasis put in each study. While Shapiro
(1996) works out the various processes of acceptance and appropriation, Schaffer (1989) emphasizes the
experimental aspect of Newton theory and the contests rather the acceptances.
8
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dissemination “evolving numerous titled gentlemen and some two hundred Cambridge
alumni” (p. 46).10
In Portugal it takes only a few months to the news of the telescope get around and in
1615 Giovani Lembo arrive at the Jesuit “Class on the Sphere” (“Aula da Esfera”) in College
of St. Antão (Colégio de Santo Antão). Lembo has been in charge of the construction of the
telescopes for the Jesuits in Rome (Leitão, 2008)
In the second half of the eighteenth century, Portugal attended a change in the
attitudes of the Jesuits towards the diffusion of newtonianism. From opposition in the
beginning, the dialogue on newtonianism among their members became customary. Since
they were in charge of education in Portuguese Universities this shift was of great importance
(Pinto & Costa, 2004, p. 328). Father Teodoro de Almeida of the Oratorian Congregation
(Congregação do Oratório), which was more willing to teach “the moderns” such as
Descartes or Newton was the author of the Philosophical Recreations (Recreações
Filosóficas), an “extensive work with ten volumes published between 1751 and 1800”.11 The
Philosophical Recreations was presented in a similar fashion as the Galileo’s Dialogue, with
Teodósio, a modern philosopher, Sílvio a peripatetic and Eugénio, a student with an open
mind. In Chapter V of the second volume “where the refraction in the Newtonian system is
explained” (Almeida, 1786) we can appreciate the tone with which Newton was regarded:
Eugénio: All this agrees beautifully with reason and with experience according to
what you said.
Sílvio: verily that is worthy of teach all this system. If is Modern only Newtonian
would be.
10
A recent account on eighteenth century optical work is developed by Darrigol (2012, pp. 109-165).
See (Pinto & Costa, 2004). For more on Portuguese Enlightenment see (Carneiro, Simoes, & Diogo, 2000).
For more on Teodoro de Almeida see e.g. (Silva, 2009), (Almeida, 2013).
11
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Teodósio: Isaac Newton is very grateful to you. I will share with him your
allegiance.(…) (p. 70)
However this passage while gave credit to Newton’s theory is misleading, for in the
Philosophical Recreations the theories of Newton, Descartes and “other moderns” are
exposed according to the Teodoro own assimilation of them and with no special emphasis on
Newton over the others. However due to the large amount of editions and the consequent
revisions, is more than conceivable that the emphasis on the various authors changed with
time.
These sets of events in seventeenth century come to settle the stage on which a
scientific research program in optics (in Lakatos sense) takes form.12
See (Raftopoulos et al., 2005). On Lakatos’ account of his SRP see for instance (Lakatos, 1968, 1970a,
1970b). An acute critique of the SRP can be found in (Feyerabend, 1981). See (Lakatos, 1970b, p. 104) for a
brief response to Kuhn and Feyerabend criticism.
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