On our now not so recent episode about Berkeley, with David Hilbert, I said in passing that idealism, in some form or other, is permanently tempting. Don't get me wrong, I don't believe in idealism. I consider myself a realist and a physicalist. Not only do I think that the world is (largely) independent of mind. I also think that the mind is ultimately just a part of that mind-independent world. That is, the mind is ultimately built out of and reducible to stuff that is not yet mind. Or so I would argue. So I don't come here to defend idealism.
What is it
Immanuel Kant introduced the human mind as an active originator of experience rather than just a passive recipient of perception. How has his philosophy influenced the world after him? John and Ken dig into the brilliantly active mind of Kant.
Kant thought that our minds had no perceptual access to the world as it but our perception was in a way warped by the limitations and idiosyncrasies of our minds. Kant calls the real world, independent of our minds, the noumenal world. The world we perceive is the phenomenal world. John claims that our total experience is a joint product of the noumenal world and the phenomenal.
Ken introduces the guest Peter Gilgen, a Professor from Cornell University. Peter Gilgen touches on the philosophical scene of Kant's time. In the mid 18th Century, rationalists (such as Leibniz and Descartes) defended a strict metaphysical system, which they claimed to build solely from reason. However, Kant's philosophy arose largely as a reaction to this tradition. Kant claimed that Humean skepticism awakened him "from his dogmatic slumbers" and that rationalists could not meet the skeptic's challenges. Inspired by Newton, Kant wanted to put "metaphysics on the secure footing of science", penning "The Critique of Reason" in the process.
Kant claimed that if an unnoticeable glass that distorted sight were put right in front of our eyes for all our life, we wouldn't be able to recognize that our sight was distorted. We can't know whether our perception as a whole is distorted by such "an invisible glass". Our perception apparatus contributes to our perception. John comments even though we see a solid desk, we know that the desk is made of atoms, atoms in turn by quarks and that the desk is mostly space. Is this the kind of perceptual distortion Kant had in mind? Peter Gilgen explains that according to Kant, our perceptual blockade is deeper than what science can reveal. Even time and space are categories our perception apparatus bring into this world.
Even though Kant thought that noumena weren't directly available, everybody had a common perceptual architecture that characterized the world. (For instance, everybody has a notion of space and time.) In a similar vein, he denied Humean skepticism about causality (which holds there is no evidence that indicates that causal laws should hold) and claimed that causality was a property of the phenomenal world.
Kant thought that even the idea that we are free is enough to grant us moral freedom and responsibility. Our intuition to judge something as not right deems morality a genuine possibility.