Kant goes down in the history of thought as a giant. Kant declared himself neither empiricist nor rationalist but achieved a synthesis of the two in his greatest work The Critique of Pure Reason (1781), which marked the end of the period of the Enlightenment and began a new period of philosophy, German idealism. Kant claimed that knowledge was impossible without accepting truths from both rationalist and empiricist schools of thought. He based his ethics on reason and said that moral duties could be deduced by all rational beings.
Kant’s Copernican Revolution
Kant noticed a problem with the empiricist manner of coming to knowledge. If all you come to know and collect are particular sensations or particular impressions, as the empiricists said, how can you arrive at necessary and universal knowledge? Put another way, how can you explain the possibility of scientific knowledge, or, more precisely, the relationship between causes and effect, which enables the mind to grasp scientific truths? Kant had an answer to the question that bridges the gap between two schools of thought — rationalism and empiricism.
Kant's own theory of knowledge reconfigures the way humans know things. Rather than saying that people are all passive perceivers observing the world, Kant believed that humans are active in knowing the world. In agreeing with his empiricist predecessors he says, “There can be no doubt that all our knowledge begins with experience. But though all our knowledge begins with experience, it does not follow that it all arises out of experience.”
Instead of an outside-in approach to knowledge of the empiricists, in which objects cause passive perceivers to have “sensations” (Locke) or “impressions” (Hume), Kant said that the categories of space and time — which he called “forms of intuition” — were imposed on experiences by the human mind in order to make sense of it. This Kant proudly called his “Copernican Revolution.” Just as Copernicus rejected the idea that the...