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.

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.

Origins in Western Philosophy

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

Objects of human contrivance exhibit

complexity and purpose.

The natural worldexhibits complexity

and purpose.

The natural worldhas been designed

by some intelligence.

Objects of humancontrivance have been

designed by someintelligence.

Similarity between objects of human contrivance and the natural world.

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 (1711-1776)

David Hume’s Critique

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).

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.

Philo’s “Weak Analogy” Objection

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 selected parts of an imperfectly known universe.

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.

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.

Returning to Paley. . . .

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.

Theistic arguments violate this principle since they attempt to explain

a finite, imperfect effect in terms of an infinite, perfect cause.

Finite, ImperfectUniverse

Infinite, PerfectBeing

David Hume (1711-1776)

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 DilemmaHume’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?