A Summary of Prolegomena --- How Metaphysics is Possible

I. Introduction

This paper serves as a brief summary of the Prolegomena, and the structure of the paper follows Kant’s three fundamental mental faculties: intuition, understanding, and reason. At the very start of the Prolegomena, Kant throws out Hume’s challenge, that cause-and-effect is nothing but what are found constantly conjoined in experience. Kant says that had this claim been true, the subject of metaphysics would have been ended. Hence, the goal of this paper is to provide the readers with a succinct answer to Kant’s final question—how is metaphysics at all possible?

II. Intuition—how is pure mathematics possible?

Kant’s first response to Hume is to categorize a priori judgments into the synthetic and the analytic kind[i], where analytic means merely explicative, adding nothing to the content of the cognition, while synthetic means ampliative, increasing the given cognition. This distinction can be seen as Kant’s first response to Hume’s attack, since synthetic a priori provides outside information that is necessarily true—that is impossible for Hume, since mathematics is no longer naively a priori[ii].

To really understand Kant’s synthetic a priori, mathematics is the best example. Kant thinks that the essential and distinguishing feature of pure mathematical cognition among all other a priori is that it cannot at all proceed from concepts, but only by means of the construction of concepts. Kant claims that mathematical intuition comes in the form of sensuous intuition, of which the form is space and time[iii]. For example, geometry is based upon the pure intuition of space; arithmetic attains its concepts of numbers by successive addition of units in time, etc. Though, following Hume, Kant also insists that we can’t have any knowledge of things as they are beyond our perception. Therefore, we cannot know how space and time metaphysically is, except as we perceive them. Why aren’t mathematics completely illusory, then? Kant’s answer is that “our transcendental deduction of the concepts of space and time” explains the possibility of mathematics. If we replace “transcendental” with “cognitive”, it is easier to see that what Kant meant was that though each person’s sensory apparatus may differ, our minds are wired to organize space in the same way. Mathematics can derive facts from the forms of human perception. This way, Kant is able to maintain that objective, universal truths are nonetheless possible.

III. Understanding—how is pure natural science possible

Like mathematics, pure natural science has an empirical component. Its concepts are taken from the visible world. And yet, it yields a priori laws, like that of gravitation. How is this possible? Kant answers this question by drawing a distinction between “judgments of perception” and “judgments of experience.”

Judgments of perception are only subjectively valid. Judgments of experience, however, combine sensory impressions with other sensory impressions using what Kant refers to as “pure concepts of the understanding”. This is where Kant resolves Hume’s doubt that we cannot comprehend by reason the possibility of causality—pure concepts of the understanding are means by which subjective, empirical judgments become universally valid, objective judgments. Kant lists four categories of judgment and twelve pure categories of the understandings[iv], which can be divided into the category of quality, quantity, relation and modality. To see how these concepts function, take causality for an example, which corresponds to the hypothetical judgments in the category of relation. Kant uses the judgment of “the sun shines, and stone grows warm” to demonstrate its mechanism. This judgment is merely of perception and contains no necessity. This is where Hume would stop and conclude that causality is beyond our perception. However, Kant says that we add to the perception a concept of the understanding, that of causality. Causality connects with the concept of sunshine that of heat, and then we can make a universally valid judgment of experience that “sun warms stone”. To Kant, the concept of cause is a concept necessarily belonging to the mere form of experience, and its possibility as a synthetic unification of perceptions in consciousness in general.

IV. Reason – how is metaphysics in general possible?

For Kant, reason functions beyond the realm of experience. To reason is to syllogize, to chain propositions together. Kant divides syllogism into three functions—categorical (which is of the form “All A is B, all B is C à All A is C”), hypothetical (which is of the form “If A then B, if B then C à If A then C”), and disjunctive (which is of the form “A or B, not A à B”). Kant then lists three pure concepts of reason (the transcendental ideas) that corresponds to the three functions of syllogism respectively: psychological idea, cosmological idea and theological idea.

The psychological idea is the concept of the soul as a permanent. It is founded on categorical syllogism, because it is the idea of stripping away layers (predicates) above the “soul” and present the soul as the ultimate subject of thinking which cannot be further represented as the predicate of another thing. Kant states that we cannot experience phenomenally the soul as a thing in itself. This idea results in paralogism. Hence, efforts such as Descartes to conclude the real existence from the experiential act of thinking is necessarily false.

The cosmological idea is founded on hypothetical syllogism, because it is the idea based on causality, or the idea of “the complete series of conditions”. For example, free-will is an idea of causality—the will is free if it is a first cause, otherwise not. The cosmological idea contains four antinomies: finitude vs. infinity; simplicity vs. composite; freedom vs. determinism; necessity vs. contingency. Kant claims that all these are false antinomies, because in all these cases, we try to draw conclusions about things in themselves using experiential contradictions. Once again, reason tries to transcend by making phenomenal claims on noumena, and hence fails. Theological idea is the idea of “the complete complex of everything that is possible”. Kant says that though reason in this case does not start from experience and err by exaggerating its ground, it proceeds to determine the possibility and actuality of all other things from mere concepts of what constitutes the absolute completeness of a things in general. Kant call this a “dialectical illusion” which arises from us trying to make the subjective conditions objective, and to make a hypothesis necessary. Reason oversteps its boundary again.

After examining all three faculties of reason, Kant concludes that if we persuade ourselves that we can by means of these transcendental ideas enlarge our cognition far beyond all possible experience, then we have misunderstood the proper application of reason. Kant claims that because we have not determined how far reason is to be trusted, and why only so far and no further, it is imperative that we come up with a formal determination of the boundary of the use of our reason.

V. Conclusion

Eventually, Kant concludes that the question now is not how metaphysics is possible, but only how we are to set about it. To do metaphysics, we need a complete table of conceptions from intuition, understanding and reason, together with what can be deduced from them, and finally their boundaries. This naturally leads us to the Critique of Pure Reason and concludes the Prolegomena.

Reference

Kant, I. (1950). Prolegomena to any future metaphysics; with an introd. by Lewis W. Beck. Indianapolis: Bobbs-Merrill.

Acknowledgment

I would like to thank Professor Kevin Kelly for the most philosophically challenging semester, and his help with this paper. I appreciate not only the well-designed reading responses which has been an immense help to this paper, but also the intense Kantian lectures that I get to enjoy, and his passion and energy for spreading knowledge and truth. Without Professor Kelly, this paper would not have been possible.

[i] See table 1 in appendix for examples of synthetic and analytic

[ii] Take Kant’s example of 5 + 7 = 12. The concept of 12 is not in the concept of 5 or 7; however, 5 + 7 = 12 is necessarily true—making this a synthetic a priori judgment rather than analytic.

[iii] Kant on space and time: For Leibniz space and time were relations among things (monads) and would have no existence whatever if there were no monads. By contrast, Newton held that space and time are infinite and independent of the physical bodies that exist in space and time. However, for Kant, space and time are based epistemologically on the nature of the mind rather than ontologically on the nature of things, either as a relation among monads (Leibniz) or as things (Newtonian absolute space and absolute time). Kant’s epistemological view of space and time provided him with a way of reconciling the opposed views of Leibniz and Newton

[iv] These tables can be found in table 2 and 3 in appendix