Kant’s Copernican Revolution

Moving the center of epistemology to the active mind

Immanuel Kant (1724–1804, rhymes with “want”) is the single most influential philosopher in history, even though you have probably never heard of him. How we think of ourselves and how we think about how we perceive the world is from Kant’s philosophy. Philosophy is a long conversation. Immanuel Kant formed a significant turning point in that conversation. And Kant was inspired by Hume, who was inspired by Berkeley, who was inspired by Locke, who was inspired by Descartes, who was inspired by Augustine, who was inspired by Plotinus, who was inspired by Plato. It really was a long conversation.

There are two eras of philosophy: before Kant and after Kant. Again, and I can’t emphasize this enough, how we think about human perception is based on Kant’s philosophy. All subsequent continental philosophy is based on Kant, and he inspired the field of psychology. You’ll see why as we explore his insights into the structure of the human mind.

The Transcendental Method

The challenge for Kant is demonstrating how synthetic a priori propositions are possible. To accomplish this, Kant engages in what he calls the “transcendental method.” It’s transcendental in that the method explores the universal nature of experience to uncover the universal and necessary conditions for understanding. If we cannot imagine experiences without a certain feature, then that feature must be a universal and necessary condition of our experiences. This was Kant’s method to identify the concepts in the mind that can extend our understanding of the world. His method is possible because he accepts that our experiences are mental depictions of external objects, not copies of them. Our active minds contribute to our experiences and our understanding.

Time and Space

The transcendental method uncovers the most fundamental structure of our experiences: space and time. Grasping time and space is so difficult because we never actually experience them but we never experience anything without them. Kant writes:

Space is not a conception which has been derived from outward experiences. For, in order that certain sensations may relate to something [external to me]…the representation of space must already exist as a foundation. Consequently, the representation of space cannot be borrowed from the relations of external phenomena through experience; but, on the contrary, this external experience is itself only possible through the said antecedent representation. Space then is a necessary representation à priori, which serves for the foundation of all external intuitions. We never can imagine or make a representation to ourselves of the non-existence of space, though we may easily enough think that no objects are found in it. It must, therefore, be considered as the condition of the possibility of phenomena, and by no means as a determination dependent on them, and is a representation à priori, which necessarily supplies the basis for external phenomena. (Critique of Pure Reason, I.I.2.2–3)

We do not perceive space — we perceive things in terms of space. The same is true with time.

Time is not an empirical conception. For neither coexistence nor succession would be perceived by us, if the representation of time did not exist as a foundation à priori. Without this presupposition we could not represent to ourselves that things exist together at one and the same time, or at different times, that is, contemporaneously, or in succession. Time is a necessary representation, lying at the foundation of all our intuitions. With regard to phenomena in general, we cannot think away time from them, and represent them to ourselves as out of and unconnected with time, but we can quite well represent to ourselves time void of phenomena. Time is therefore given à priori. In it alone is all reality of phenomena possible. These may all be annihilated in thought, but time itself, as the universal condition of their possibility, cannot be so annulled. (Critique of Pure Reason, I.II.5.1–2)

Space and time are the intuitions that make our understanding of objects possible. They are the conditions by which all of our experiences conform. Try to imagine the color green. You cannot image “just” green, but a green something that has qualities of both space and time. Remember Berkeley’s argument that we can’t conceive of abstract ideas? We can add to it that we cannot imagine green in the abstract, and we cannot imagine it outside of space and time.

Kant refers to space and time as “the pure elementary notions of the Sensibility.” (Prolegomena, 39.4) Time and space are forms of inner sense that structure our depictions of objects. Without that structure, the contents of our minds would be no more than what Hume called the flux of impressions. Time and space are synthetic a priori judgments that structure our perceptions and allow us to have sensible experiences. We do not experience space or time in and of themselves — only objects in space and time. Space and time are intuitions that make experiences possible, but we do not learn them through experience; they are always there. Human perception is impossible without them.

The Categories of Understanding

Space and time are just the beginning of what the transcendental method uncovers. Kant also says that our mind has a set of further categories that structure our mental depictions of external objects. He calls them Pure Conceptions of the Understanding, or Categories. The Categories are, like space and time, conditions by which our understanding is possible. Our mind’s depictions of objects are structured and made sensible in space and time, and the Categories do what Kant describes as a synthesis

by which alone the elements of our cognitions are collected and united into a certain content.…a blind but indispensable function of the soul, without which we should have no cognition whatever, but of the working of which we are seldom even conscious.” (Critique of Pure Reason, I.III.6.1)

The Categories are what turn mere collections of sensations into depictions of things. We never experience the Categories because they are a priori — they are independent of experience because they are a necessary precondition of experience. We don’t experience what the Categories do; we experience only their effects.

Kant’s bold claim is that the Categories are synonymous with all possible logical functions and judgments. In other words, they are how we think, and we cannot think otherwise than through their a priori synthesis. Kant says he calls these pure conceptions “Categories” after Aristotle’s Categories because, Kant says, his purpose is identical with Aristotle’s, but executed differently.

The concepts in this table are what the human mind contains a priori. They are literally how we think about and make sense of our mental depictions that we perceive in terms of space and time. They are not what we think about; they are how we think. They are thinking at the most basic level, the logical a priori synthetic judgments by which we understand anything and everything. Kant said that space and time are the faculty of Sensibility and the Categories are the faculty of Understanding. Knowledge is the product of these two faculties of the mind.

Kant’s discussion of how the Categories give us understanding is complex — so complex he had to write a second book (the Prolegomena) to explain his first book (Critique of Pure Reason) on the subject. Suffice it to say for our purposes here that a simple example can show how the Categories unite our depictions into one conscious understanding of objects.

Imagine a dot. Just one dot. Right away you are using the logical judgments of the Categories, starting with Unity to understand that you are considering one dot. You didn’t need to think hard at all; your mind is predisposed with that capability. Now imagine a second dot. That’s using Plurality to go beyond one dot to a plurality of dots. If I draw seven dots and ask you how many dots there are, you can answer because you can Measure the Quantity of dots as a Whole as equaling seven. If I then ask you to draw a circle around three of the seven dots, you can do that because you logically Limit the Reality of the dots, choosing three while Negating the other four dots. If this sounds very simplistic, that’s the point. This is the most basic level of human thought. We don’t learn this — we know this a priori — but we can use these judgments to gain knowledge of the world, so these propositions are synthetic propositions.

The Categories of Modality are also basic forms of thought. They are logical modes by which we judge objects and ideas. They come in pairs, and each pair of modalities underlies substantial questions that philosophers have debated for centuries. We never learned these modalities through experience; we think in terms of them. To think that something is possible or impossible, that it exists or does not exist, that it is a necessary or contingent occurrence means to think in terms of synthetic a priori judgments of the Categories.

The Categories of Relation deserves special attention because they answer Hume’s serious objections. Kant agrees that we do not have sense experience of substance or causality, but the Category of Inherence and Substance forms a unity out of our various perceptions of qualities that enables us to form concepts such as “tree,” “dog,” and “human.” True, we cannot say what the reality beneath these qualities is, but that’s not the point. Substance is a logical function and judgment that orders the flow of sensations into coherent objects in our mind. Perhaps the idea of “tree” is, as a skeptic could say, nothing but an idea in our mind, but that is all we have to work with, and it is how we think about our sensations. Hume said our idea of necessary causality is simply a product of habit. Kant replied that causality is a logical a priori synthetic judgment by which we understand the succession of events that we perceive. In the billiard ball example, Hume said that we do not witness causation; we witness only three impressions. Kant agrees and said that our mind contributes the concept of Causation and Interaction to the sense impressions to make sense of the events that we witness. We cannot imagine a world in which there is no causal order, no interaction between objects (Leibniz’s bizarre theory aside), but these a priori concepts structure our experiences and enable understanding. The Categories are how the human mind is structured. Kant says that God or horseflies may experience the world differently because they may have different Categories, but all human beings have the same Categories and thus experience the world in the same basic way.

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