The Classical Design Argument
Inferring God’s Existence from
“Design Features” of the
Universe
Arguments for God’s Existence
The project of developing arguments for God’s existence
is typically designated natural theology.
Theology – discourse about God
Natural –a mode of discourse that engages the natural
order, including both the human intellect and the
physical cosmos.
Hence, natural theology typically stands in contrast to
revealed theology, discourse about God that proceeds
from an analysis of the teachings of sacred scripture as a
purported special kind of revelation from God.
Origins in Western Philosophy
Natural theology originated among Pre-Socratic
philosophers in the 6th century BCE in their effort to
understand plurality and change as fundamental features
of the cosmos. The most elaborate arguments are found
in Aristotle’s Physics and Metaphysics.
Natural theology was appropriated by the Jewish and
Christian religious traditions beginning around the 3rd
century CE and subsequently also by Islam shortly after
its emergence in the 7th century.
Arguments for God’s existence were widely discussed
throughout the medieval period, roughly from the time of
St. Augustine (4th-5th century) to the beginnings of the
European Renaissance in the 14th/15th century.
In the modern period, natural theology has been endorsed
by the Catholic Christian tradition and many streams of
Protestant Christianity.
It has also been the subject of enduring philosophical
exploration, as is reflected in the works of the great
modern philosophers, e.g., Descartes, Leibniz, Hume,
and Kant.
Kant’s critique of natural theology in the 18th century and
the rise of Darwinism in the 19th century generated
significant skepticism about natural theology that
continued until natural theology re-emerged in the middle
of the 20th century as the result of developments in both
philosophy and the sciences, especially cosmology.
The Classical Design Argument
“If, therefore, the products of nature are better than
those of the crafts and if the crafts do nothing
without the use of reason, then nature too cannot be
held to be devoid of reason.
“When you look at a statue or a painting, you know
that craftsmanship was applied. . .when you gaze on
a sundial or a waterclock, you understand that the
time is told as a result of craft and not the result of
chance.
“So what sense does it make to think that the
cosmos, which contains these very crafts and their
craftsmen and all else besides, is devoid of
deliberative ability and reason?”
(Cicero, De Natura Deorum, 2.87)
The Stoic Argument
(1)Whatever is ordered is intelligible.
(2)Whatever is intelligible is a mind or the work of
intelligence.
So
(3) Whatever is ordered is a mind or the work of
intelligence.
(4) The cosmos is ordered.
So
(5) The cosmos is mind or the work of intelligence.
The Design Argument
John Ray
(1628-1705)
William Derham
(1657-1735)
William Paley
(1743-1805)
The Watchmaker
A watch is an intricate and complex
system well-suited to the task of
measuring time.
We regard the watch as the product of
some intelligent being on account of
its complexity and functionality.
Living organisms are intricate and
complex systems well suited to the
tasks of reproduction and survival.
We should conclude that all living
organisms originate from some
intelligent being.
The Analogical Organismic Design
Argument
The natural world
exhibits complexity
and purpose.
The natural world
has been designed
by some intelligence.
Similarity between objects of human
contrivance and the natural world.
Objects of human
contrivance exhibit
complexity and purpose.
Objects of human
contrivance have been
designed by some
intelligence.
The Basic Argument Stated
• Watches are produced by intelligent design.
• Organisms are similar to watches to degree
p
p[===============================
• Organisms were produced by intelligent
design.
“P” represents the degree of similarity between watches and organisms and it
also represents the probability of the conclusion (below the double line)
given the two statements (premises) above the double line. The greater the
similarity between watches and organisms, the greater the probability that
organisms were produced by intelligent design.
David Hume’s Critique
David Hume (1711-1776)
In his famous Dialogues on Natural Religion,
David Hume launched what is arguably the first
and most well known systematic attack on the
design argument for God’s existence.
Cleanthes – the advocate of the Paley-style design
argument
Demea – an advocate of an alternate methodology,
the cosmological argument, which seeks to prove
God’s existence the fact of the universe’s existence,
rather than its design features.
Philo – the skeptic (more or less Hume’s own voice
in the dialogue).
Philo’s “Weak Analogy” Objection
The design argument is an analogical argument and
thus requires a degree of similarity between
“human artifacts” and “the universe” that we are
not warranted in assuming.
Philo speaks of features of the universe, though he
switches at different points to more “local”
phenomena associated with organisms.
Cleanthes’s Basic Argument:
(C1) Houses are the product of intelligent design.
Therefore, it is probable that:
(C2) The Universe is the product of intelligent design.
Philo’s Formulation of the Analogical Argument:
(1) Object A has some property P.
(2) Object A and object B are overall similar to some degree
N.
Therefore:
(3) Object B has property P.
Philo argues that the probability of (3) is directly proportional
to the value assigned to N. The greater the similarity between
A and B, the greater the probability that B has property P
based on the fact that A has property P.
Cleanthes’s argument more precisely must take this form:
(P1) Houses have the property of being produced by intelligent
being.
(P2) Houses and the universe are overall very similar to each
other.
Therefore: it is probable that
(C3) The Universe has the property of being produced by
intelligent design.
Philo rejects (P2) and presents the following counter argument:
(P1) Houses have the property of being produced by intelligent
design.
(P2*) Houses and the Universe are NOT overall similar.
Therefore, it is improbable that
(C3) The Universe has the property of being produced by
intelligent design.
I. Philo’s Argument for (P2*) –
Dissimilitude
Houses and the Universe are dissimilar because (a) we can
observe houses being made and thereby link them to their
causes through the constant conjunction of cause and effect,
but (b) since the Universe is unique we have no basis to link
it to any cause.
II. Philo’s Defense of (P2*)
We are not warranted in concluding that the cause of the
whole universe is overall similar to the parts of the universe
exhibiting reason or intelligence as their mode of operation.
This is a fallacious inference (fallacy of composition)
attributing to the whole what is characteristic of only
A Likelihood Formulation
of
the Intelligent Design Argument
Likelihoodism
• “Likelihoodism” is one approach to
confirmation theory, that is, the study of
formal features of evidence assessment.
• The central principle of Likelihoodism is
the Law of Likelihood:
Evidence e favors hypothesis h1 over h2
just if the probability of e is greater given
h1 than it is given h2.
Pr(e | h1) > Pr(e | h2)
The Likelihood of a Hypothesis
• To speak of the “Likelihood” of a hypothesis is to
speak of how probable the hypothesis makes an
observation, not how probable the observation
makes the hypothesis (i.e., the so-called posterior
probability of a hypothesis).
• The likelihood of a hypothesis can be very high
(even unity), even if the probability of the
hypothesis itself is very low.
• Law of Likelihood doesn’t tell us what we should
believe. It tells us what the evidence says,
specifically whether evidence favors one
hypothesis over another competing hypothesis.
Likelihood Formulation of the Intelligent
Design Argument
•
•
•
Paley’s central claim can be construed as: the
probability of complex adaptations (A) is greater
given intelligent design (ID) than it is given
chance (C).
Pr(A | ID) > Pr(A | C)
The argument does not say the existence of an
intelligent designer is probable, only that
complex adaptations provide evidence that favors
the intelligent design hypothesis over the chance
hypothesis.
Paley’s Watch Argument
• A watch has features G1 . . . Gn.
• Pr(the watch has features G1 . . . Gn | chance) = tiny.
• Pr(the watch has features G1 . . . Gn | intelligent
design) > tiny.
• The law of likelihood
___________________________________________
• The watch’s having features G1 . . .Gn favors
intelligent design over chance.
Paley’s Organismic Argument
• The eye has features F1 . . . Fn.
• Pr(the eye has features F1 . . . Fn | chance) = tiny.
• Pr(the eye has features F1 . . . Fn | intelligent design)
> tiny.
• The law of likelihood
___________________________________________
• The eye’s having features F1 . . .Fn favors intelligent
design over chance.
Strengths of the Likelihood Argument
1. It does not depend on a strong
resemblance between watches and
organisms. So it’s immune to Hume’s
weak-analogy objection.
1. The conclusion is modest: “the evidence
favors intelligent design over chance.”
Three Critical Responses to the Likelihood
Organismic Design Argument
1. Superior Hypothesis Objection
Paley was correct that
Pr(A | ID) > Pr(A | C), but Paley could not have
known that
Pr(A | Darwinian evolution) >> (A | ID)
While the phenomenon of complex adaptation
evidentially favors intelligent design over
chance, complex adaptation greatly favors
Darwinian evolution over intelligent design.
Charles Darwin (1809-1882) succeeded in showing
that complex forms of life could evolve from simpler
forms of life through the biological law of natural
selection operating on random variations thrown up
by nature. Once this is filled out into a more robust
theory of evolution, the data, including complex
adaptations, are not so surprising.
2. Falsification Objection
•
While the first critical response depends on the merits of
Darwinian evolution, there is a second criticism that does
not.
•
Stephen J. Gould has argued that intelligent design leads
us to expect that the world would not have features that it
actually does have. So it’s a bad theory, quite
independent of how good of a theory Darwinian
evolution is.
•
Example: the Pandas “thumb” (wrist spur bone) is a very
inefficient tool. An intelligent designer surely could have
and would have come up with a better anatomical
structure for Pandas to acquire and eat their food.
Combining First and Second Objections
• Gould in fact combines the first and second
criticism.
• Perhaps. . .
Pr(Complex adaptation | Intelligent design) > (Complex
adaptation | Chance),
• But the relevant point would be:
Pr(Imperfect adaptation | Darwinian evolution) >> (Imperfect
adaptation | Intelligent design)
• Imperfect adaptations are to be expected given Darwinian
evolution, but they are not to be expected given the
hypothesis of intelligent design.
Third Objection
3. Inscrutable Predictive Power Objection
•
Gould’s objection depends on the assumption that a
designer would have had the power to prevent the Panda
from having a wrist spur bone and would have had the
goal of not giving this device to the Panda.
•
But . . . Gould is not warranted in attributing to the
designer this ability and goal, for there is no way to
independently test such assumptions.
•
So there’s no justification for claiming that the Panda’s
“thumb” is evidence against an intelligent designer.
Problem for Intelligent Design
• The criticism of Gould also applies to the
intelligent design advocate.
• If Gould is not justified to claim a low likelihood
for the intelligent design hypothesis, the intelligent
design advocate is not justified in claiming a
likelihood for it that is superior to Darwinian
evolution.
• Why? We’re not justified in any claim about the
likelihood of intelligent design.
Returning to Paley. . . .
In the watch argument, the crucial premise is:
Pr(the watch has features G1 . . . Gn | intelligent
design) > tiny.
How do we know this?
Only because we operate with independently testable
assumptions about the goals and abilities of human
designers.
Paley knows that human designers have the required
abilities and goals that make the features of the watch
probable.
The Problem of Inscrutable Predictive
Power
In the organismic design argument, the parallel
crucial premise is:
Pr(the eye has features F1 . . . Fn | intelligent design)
> tiny.
How do we know this?
Unlike human designers and watches, we do not know what
the abilities and goals of an intelligent designer would be
for features of organisms. Some such assumptions would
result in the probability of the observational data being
zero; in other cases, unity. But none of the assumptions is
independently testable.
Summary
• The hypothesis of an intelligent designer predicts
nothing about the features of organisms.
• It can only make such predictions if we add the
appropriate kinds of auxiliary assumptions, but
none of these auxiliary assumptions is (presently)
independently testable.
• What is the comparative likelihood of
Pr(complex adaptation | intelligent design)?
• Who knows? It’s simply inscrutable.
The Argument Defeated
We cannot justifiably claim that complex
adaptation is evidence for intelligent
design.
Raising David Hume. . . .
Another Humean Objection:
We Cannot Infer that “God” is the Designer
Even if we are permitted to infer that the universe is
designed, we cannot conclude that God is the designer.
Philo’s first “weak analogy” objection depended on an
assumption about causation, namely that we cannot
postulate unobservable causes of observational
phenomena, for cause and effect requires the constant
conjunction of observable events.
Philo’s second “it’s not God” objection depends on another
principle of causation, the principle of causal
proportionality.
Principle of Causal Proportionality: We
must not ascribe to a cause anything
beyond what is minimally required to
account for the effect.
David Hume (1711-1776)
Theistic arguments violate this
principle since they attempt to explain
a finite, imperfect effect in terms of an
infinite, perfect cause.
Finite, Imperfect
Universe
Infinite, Perfect
Being
I.
We cannot infer that the designer is infinite in
power, knowledge, and goodness because only a
being with limited power, knowledge, and goodness
is required to produce a finite universe.
II. We cannot infer that the designer is perfect because
an imperfect designer would suffice to produce the
universe, especially since (a) the universe exhibits
many imperfections and (b) we know of many cases
where designers are very imperfect (indeed, even
stupid!) and yet despite this produce complex,
useful, and beautiful things.
III. We cannot infer that the designer is one because
many agents working together or individually would
suffice to produce the universe.
Philo’s second objection highlights the range
of possible designer scenarios that would
suffice for explaining design.
Given that we have no principled way of
selecting the more probable scenario from
among the competitors, we can’t even infer
that God probably exists.
Hume’s Dilemma
Hume’s challenges to the design argument may be succinctly
stated as a logical dilemma:
1. Either the designer of the universe is very much unlike the
universe or the designer of the universe is very much like
the universe.
2. If the designer of the universe is very much unlike the
universe, then the degree of dissimilitude between the
designer and the universe prevents actually inferring a
designer of the universe.
3. If the designer is very much like the universe, then the
degree of similitude between the designer and the universe
prevents inferring that God is the designer of the universe.
So:
4. Either we cannot infer a designer or we cannot infer that this
designer is God.
“I have no need for that hypothesis.”
- Pierre-Simon Laplace
Laplace’s answer to the question posed to him
by Napoleon Boneparte as to what place God
had in his theory of the formation of the solar
system.
Is there a need to appeal to God to explain
the universe?