What is possible in metaphysical thought and what is not according to Immanuel Kant?
"What most clearly is not possible is any legitimate synthetic a priori judgment about things in themselves. The only thing that justifies the application of regulative principles in mathematics and natural science is their limitation to phenomena. Both sensible intuition and the understanding deal with the conditions under which experience is possible. But the whole point of speculative metaphysics is to transcend experience entirely in order to achieve knowledge of the noumenal realm. Here, only the faculty of reason is relevant, but its most crucial speculative conclusions, its deepest convictions about the self, the world, and god, are all drawn illegitimately."
According to Kant, it is vital always to distinguish between the distinct realms of phenomena and noumena. Phenomena are the appearances, which constitute our experience; noumena are the (presumed) things themselves, which constitute reality. All of our synthetic a priori judgments apply only to the phenomenal realm, not the noumenal. (It is only at this level, with respect to what we can experience, that we are justified in imposing the structure of our concepts onto the objects of our knowledge.) Since the thing in itself would by definition be entirely independent of our experience of it, we are utterly ignorant of the noumenal realm.
Thus, on Kant's view, the most fundamental laws of nature, like the truths of mathematics, are knowable precisely because they make no effort to describe the world as it really is but rather prescribe the structure of the world as we experience it. By applying the pure forms of sensible intuition and the pure concepts of the understanding, we achieve a systematic view of the phenomenal realm but learn nothing of the noumenal realm. Math and science are certainly true of the phenomena; only metaphysics claims to instruct us about the noumena. Quote from: http://www.philosophypages.com/hy/5g.htm
I agree with the above quote with a caveat. Reality in Kant’s day had a different meaning from today. For one thing Quantum mechanics had not been thought. The idea’s associated with a Quantum world such as non-locality; super position and entanglement were unheard of then. For another the internet had not been created. Today reality I think relates more to the physical world the world of our experience and actuality relates more to the noumenal world of theories of multi universes and Universal mind state.
And here in lies the conundrum.
We as a society (Western particularly) are so entrenched in the idea that there must be reason, rational thinking and logical argument to "prove or disprove" anything have hoisted ourselves collectively by the metaphorical "seat of our pants" up so far our feet can no longer feel the ground of actuality.
Perhaps the greatest difference for me is that a world that has always existed beyond reason is now freely able to be discussed on forums such as this by anybody. I can also post my blog or book on the internet without fear of ridicule or personal attack. Yeah right! Ask Salman Rushdie or Julian Assange about that!
So what are the limits of reason today?