Born in the 18th Century, Immanuel Kant was a Prussian metaphysician and was an important part of the Enlightenment. Born in Konigsberg, the then Regional capital of Prussia, he never travelled more than 10 miles away from it. It is something that influenced his philosophy for the rest of his life, because as the capital of Prussia, life in the city was very idealistic, orderly, and this coupled with the fact that he spent from the early age of 16 the rest of his career in an University. As we all know, Universities are very idealistic, holistic, and pure places which led to him having a very refined, yet very structured, strict, and sometimes too unrelenting and idealistic philosophy.
This is reflected in his most influential, and famous work, “Kritik der reinen Vernunft” or “The Critic on Pure Reason” which is considered by some as the most significant work ever made in the area of Metaphysics, and Epistemology in modern philosophy. It offered what he and others termed as non-empiricist critique of rationalist philosopy or the Copernican Revolution. What he rejected in essence is that all a priori knowledge (That knowledge independent of experience) must be analytical (derived from logic alone). For example you could say that an intelligent man is a man, or is intelligent, but you can’t say that an intelligent man is happy, because you aren’t acquainted with the Intelligent man, so therefore you can’t through logic come to the conclusion that the intelligent man is happy. So, in short, a priori logic does not create new knowledge, as you must already know that knowledge to come to that conclusion.
However, Kant brought into the equation the element of sensibility, and he argued that there are 2 branches of a priori derived conclusions, one which is analytical like before (A line is straight), and one which is synthetic a priori, which means that by using prior knowledge and coming to a logic conclusion but as a result creating new knowledge. He argued that something that was previously considered analytical like 2+2=4, is still a priori, but also synthetic at the same time, because it creates new knowledge. As a result of this, he summarised and proposed that existence, and matter, and space are not based on previous knowledge, but the synthesis on our preconditions, and what we previously knew.
This is in our modern Zeitgeist because we know perceive people to have the ability to synthesise new knowledge out of previous knowledge. This is because originally people thought that everything you knew was came from experience (empiricism), and experience only. But, now, he [Kant] amends that and says that you experience something, which is an a posteiri knowledge source, and with that prior knowledge you can synthesise new knowledge from perception.
I do agree with his argument, because it is an attribution to Human greatness, that human potential is limitless, and non-restrictive, and that we can know anything if we really think, and work it out, instead of the previous misconception that we are only limited to what we can experience whether by reading books, or going out exploring, but that’s it, and that we can’t through reason derive new knowledge.