Two Miscellaneous Objections
The Big Picture
Kant's appraisal of the design argument is not entirely negative. Kant accepts that the design argument is valuable and successful in at least two ways. First, the design idea has an important heuristic (inquiry-guiding) role to play within science. The design argument "suggests ends and purposes in nature" that we would not otherwise be looking for. Unlike many philosophers of science since Darwin, Kant believed that it is a legitimate and important function of science to investigate the overall design of nature. He implicitly rejects the conception of science that limits it to the study of impersonal, unguided and purposeless forces. Moreover, Kant believed that the design argument is important for science because it encourages us to posit a unity to all of nature. This principle of natural uniformity is a crucial presupposition of scientific inquiry. Thus, Kant sees the design argument, not as an enemy or obstacle to scientific progress, but as foundation and guide to the scientific enterprise.
Second, Kant believed that the design argument has an important religious function: it can quieten our doubts (p. 521) and prepare the understanding for theological knowledge. Kant believed that this theological knowledge can be acquired only through the investigation of moral principles. However, he recognized that the design argument provides important aid and support to religious faith.
Kant makes two important qualifications Theto his positive assessment. First, he insists that we cannot claim "apodeictic certainty" for the conclusion of the argument. Apodeictic certainty means a degree of certainty that is final, irreproachable, and absolute, the kind of certainty that attends mathematical proof. Kant recommends that the design argument be accompanied with a more "moderate and humble" tone.
Secondly, Kant points out that the conclusion of the argument is somewhat indeterminate. We can conclude that the creator of the world is "very great, astounding, immeasurable". These are, however, merely vague honorifics, indicating that God is much greater than we, without specifying precisely how great He is. In particular, the design argument does not demonstrate God's infinity. Consequently, according to Kant, it cannot "serve as the foundation of theology", which in turn can act as the "basis of religion".
These qualifications seem quite reasonable. Apodeictic certainty is unavailable in science, and we must be content within metaphysics with even less certainty than can be found in the special sciences. As I argued in the last lecture, the infinity of the creator is the most probable hypothesis, but it would certainly be an exaggeration to claim that we could "demonstrate" God's infinity on the basis of the design argument alone.
Kant finds the design argument wanting because he has very inflated expectations of philosophical theology. He is looking for a philosophical theory that can form the "foundation" of theology, and Kant sees theology as the "basis" of religion itself. It would be more reasonable to look to theology to provide us with greater understanding of religion, but to base religion on theology would seem to be reversing their priority. Moreover, it is unclear that theology is in need of a philosophical "foundation". Instead, we should hope that, at best, philosophy and theology are able to provide some degree of mutual illumination.
Kant raises two objections directed specifically to the design argument. The first is a variant on the infinite regress objection posed by Hume. Kant proposes a dilemma: either God is a member of the chain of natural causes, or God stands entirely outside that chain (p. 519). Kant claims that in the second case, human reason cannot reach the conclusion that God exists. In the first case, an infinite regress looms, since the existence of a finite, contingent creator would call for explanation in terms of what caused it to exist. Kant's treatment of the first horn of the dilemma seems sound. However, Kant offers little argument for believing that the existence of an infinite, necessary cause is beyond the scope of human reason.
Second, Kant argues that the design argument proves only that the form of the world has been caused. It does not demonstrate that the matter or substance of the world is similarly contingent. This objection seems outdated in light of recent cosmology. According to modern physics, including general relativity, the form and matter of the world are inseparable. Both have their origin in the Big Bang singularity.
As we have seen repeatedly, Kant held that human reason cannot reach certain conclusions about the real (or "noumenal") world. Instead, our natural or scientific knowledge can reach no farther than the phenomenal world, the world of empirical appearances. In particular, our inferences from effects to causes have no validity beyond the bounds of the phenomenal world. This thesis Kant calls "transcendental idealism".
There seems to be some confusion in Kant's mind about the exact boundaries of the phenomenal world. Similar ambiguity besets such words as "empirical" and "possible objects of experience". Kant denies that a necessary, infinite first cause can belong to the empirical or be a possible object of experience. If by "object of experience", Kant means "directly perceivable by the unaided human senses", then it is clear that God cannot be an object of experience. However, it is wildly implausible to claim that our scientific knowledge is limited to the possible objects of experience in this sense. This would mean that atoms, genes, galaxies and other theoretical objects would be outside the bounds of knowledge.
If, in contrast, Kant means by "objects of experience" "objects whose existence can be inferred from sense experience", then Kant is merely begging the question when he denies that God is a possible object of experience.
Still, it would be troubling if God, along with electrons, galaxies, trees, rocks and clounds, were merely an appearance. Why does Kant deny reality to the objects of scientific knowledge? The fundamental reason for this denial was Kant's concern to preserve a chasm between natural science and philosophy. Kant foresaw that the progress of natural science would eventually threaten the existence of free will and the objectivity of moral value. Kant attempted to "limit (scientific) knowledge in order to make room for (ethical) faith". For example, Kant's solution to the conflict between determinism and free will was to place determinism in the world of appearances and free will in the empirically inaccessible world of reality.
Obviously, Kant's drastic solution is unnecessary if either determinism is not the inevitable result of scientific inquiry or free will and determinism are not incompatible. I have already argued that determinism is not inevitably associated with causal explanation, and we have seen that recent advances in science (especially quantum mechanics) have further disassociated natural science from determinism. In future lectures on the problem of evil, we will briefly examine the question of the compatibility of free will and natural causation.
Kant had at least two further reasons for transcendental idealism. First, there are the antinomies of pure reason. Kant believed that reason fell into several inevitable contradictions whenever the distinction between the phenomenal and noumenal world is ignored. We have already examined the First Antinomy and found the proof of the antithesis wanting. Most modern commentators find similar defects in the other antinomies.
Second, Kant argues that transcendental idealism is the best explanation for the existence of our "synthetic apriori" knowledge. Following Leibniz, Kant divides all propositions into two categories: analytic and synthetic. In analytic propositions, the predicate is "contained in " the subject term. A proposition of the form "all A's are A's" is clearly analytic. So are propositions of the form "all AB's are A's". Finally, a proposition that can be converted into one of these forms by means of substitutions licensed by definitions are also analytic, like "all triangles have three sides" or "all bachelors are unmarried". All other propositions are synthetic, including laws of logic or arithmetic that do not have a form that fits the analytic pattern. Knowledge of an analytic proposition is analytic knowledge -- all other knowledge is synthetic. Kant believed, with Leibniz, that analytic knowledge is plain and unmysterious.
Knowledge can also be divided into apriori and aposteriori knowledge. Aposteriori knowledge is knowledge that is based on the specific contents of actual sense experience. Apriori knowledge is all other knowledge. Following Hume, Kant takes all aposteriori knowledge as unmysterious and self-explanatory. This leaves synthetic apriori knowledge as potentially problematic. Hume simply denied that we have any synthetic apriori knowledge at all. Kant believed that we clearly do: our knowledge of logic, arithmetic and the principle of causality are all synthetic and apriori.
However, Kant agreed with Hume that the very possibility of synthetic apriori knowledge is in need of explanation. Kant rejected an explanation in terms of "pre-established harmony". In particular, he felt that it would be inappropriate to appeal, as Descartes did, to the truthfulness and benevolence of God in validiting the veridicality of our natural beliefs. Consequently, Kant felt that the only possible explanation of our synthetic apriori knowledge is the one offered by transcendental idealism. Our synthetic apriori knowledge is limited to the world of appearance: it has no validity in relation to the world of reality. Our synthetic apriori knowledge is valid with respect to the phenomenal world because this world is a world of our own making, a world that our minds have constructed, using the principles of our own understanding as constitutive archetypes. We can know, apriori, that these principles are true of the world of appearances because we (unconsciously) put them there. They are contained in the original blueprints of the phenomenal world within our own mental constitution.
A thoroughgoing consideration of Kant's transcendental idealism is beyond the scope of this course. However, I will briefly sketch an alternative account of our synthetic apriori knowledge, including our knowledge of the principle of causation. This alternative returns to the boostrapping metaphor I used in an earlier lecture. If we suppose that our synthetic apriori beliefs have some slight justification prior to all empirical confirmation, then we can use empirical justification to propel an upward-moving, virtuous spiral. At each turn of the spiral, the degree of justification of the apriori beliefs is increased. This increased degree of justification of the synthetic apriori foundations gives empirical investigation still greater power of justifying those foundations. As long as actual experience cooperates, the level of justification continues to rise until the beliefs reach the status of genuine knowledge.
Hume and Kant would probably object to the very first step. They would contend that our synthetic apriori beliefs have absolutely no justification, if they are taken as referring to the real world, beyond our own minds. However, I would suggest that the mere truth of these beliefs, assuming that they are true, provides them with some slight degree of justification. Furthermore, the fact that they are natural beliefs, beliefs in accord with the natural function and proclivity of the human mind, also provides them with a degree of warrant.