On some level, all important philosophy changes the assumptions behind a problem wrestled for decades or centuries by philosophers. In the case of Kant, he changed the assumptions behind a surprising number of philosophical problems.
- What can we know?
- Can we know the objective truth?
- Can we ground the truths of math/geometry?
- Can we ground science, such as Newton’s laws, some of which cannot be known immediately through observation?
- Does the world exist?
- If a tree falls in the forest and no one is there to hear it, does it exist?
- What can we know about metaphysics?
- What can we know about cause and effect?
- What can we say about God?
- What can we say about morality?
- If the world is deterministic, how can we be free?
- What is “the self”?
With Kant many paths converge into a single, brilliant, comprehensive system that established new distinctions, possibly answering all of these questions (though, not without many internal inconsistencies and unanswered questions). Many people are unconvinced by Kant’s answers, but respect him enough to argue against him. Although it is not as simple I make it out to be, all of Western philosophy finds Kant in its family tree, spanning from the socio-historical feminist, Marxist, or postmodern thinkers, to the very scientific, rational English-speaking ethicists and metaphysicians.
In this text Kant attempts to understand the ways in which humans think and perceive the world, in order to clarify what they can know. He blended two streams of thought; Rationalism (Descartes, Leibniz, Wolff) which assumed we could use reason to know the world, and Empiricism (Locke, Berkeley, Hume) which argued that we learn about the world through experience. Kant looked for a third way, that all knowledge is grounded in experience, and we can make limited metaphysical claims through reason, but experience is impossible without filters that make the world intelligible. Consequently, we do not experience the world as it is in itself. We can make rational judgements (extrapolations) based on the knowledge we have gained through direct experience, but we must admit that without access to the “thing in itself,” without access to knowledge beyond the reach of the act of sensuous experience itself, we have limited access to metaphysical truths.
One of the most important questions of Modern philosophy: what is the self? Descartes described the self as a thinking self; a self that is not necessarily tied to the physical world. Kant does not claim to know what a self is, apart from what must be presupposed, what he has experienced, and what can be extrapolated from these presuppositions and experiences. One experiences the world, from the “manifold,” multiple perspectives and senses over time, through the framework of space and time. We cannot know about the thing in itself, but we make the object intelligible by presupposing space and time. We cannot know that space and time are real, but we can experience the world by interpreting the world through the framework of space and time (and a few other things). By unifying the experiences from the senses into representations, one learns things about the object, and about the world. Once one has learned things (intuition) he or she can make judgements, unifying multiple representations into new representations (classical logic, analytic), or by extrapolating from representations, with the use of the imagination, into new representations (transcendental logic, synthetic).
The “self” arises from transcendental logic, which recognizes that the experience of objects necessitates a unity of the manifold, which necessitates the unity occurring in a thinking consciousness. Since the consciousness coexists with the experiences of the object, they become “my” experiences. In other words, a self is dependent upon the existence of an actually existing outside world. Metaphysically Kant is not calling the self a spiritual being in the way Descartes does. Kant is describing the self phenomenologically. And he argues that his phenomenological claims are not merely subjective. They hit on the objective truth by avoiding claims like “It, the body, is heavy,” instead making claims like “If I carry a body, I feel a pressure of weight.” He is not describing the “thing in itself” of the “self.” He is describing what can be known about reality, recognizing the role of the translation of experience into the framework of space and time. We cannot know metaphysically what a self is. We can only describe a self through a universal, but phenomenological approach.