In his "Critique of Pure Reason," Immanual Kant attempts to explain how rationality can reason absolutes truths of knowledge, particularly concepts of intellectual representation such as space and time, without having to rely on the senses, which would be more in line to what Hegel and the empiricism school of thought.
One of the main concepts Kant tries to explain is a priori, or to put it another way, universal truths of sensible representations and what their role in our cognition is. Kant refers to this as transcendental knowledge that deals with absolute truths outside of empiricism. Kant continues by explaining that if one were to sit down and fail to "concept", or find representation of an object without experiencing its faculties, then that knowledge falls under empiricism, or experiences through our senses. Kant is kind of merging two schools thought, first by saying that we all have some a priori knowledge already within us. Kant uses space and time as examples of how we universally already know or represent what space and time is without having to empirically experience it, then based off of how our a priori representations of how space and time work, we "make possible" representations of objects that we are spatially aware of (not that we still don't empirically represent what an object is), before finally attempting to explain objective validity a priori for intellectual representations into twelve categories. Basically if the representation fell into one of the twelve categories of objective validity, it is a priori or necessary universal knowledge outside of empiricism, and if the representation does not fall into the twelve categories then our minds are passively sensing, or a posteriori. Kant agreed with Hegel for the most part in that empirical knowledge was important, but Kant stood his ground that without the universal absolutes of a priori, there is no knowledge or experience.
