Transcendental experience
At the center of this complicated book is the simple argument that human experience is more than meets the eye, so to speak. There is more to the human experience of consciousness than simple sense perception implies, but he does not mean that in some far-out religious way. He means that experiencing anything at all is predicated on an unseen question: we exist, but what is reality and existence itself? Are we sure we are not embedded in a limited experience of a more sophisticated reality that we do not perceive. Through experience comes a philosophy of transcendentalism.
Sense perception
The imagery of sense perception constitutes the subject of the book. From the realities of sense perception and the Cartesian idea that we are experiencing in the first place, Kant is able to draw logical conclusions from the faculties of perception to deduce a metaphysic. This abstraction of life's meta-narrative is the major quality of his philosophy. That philosophical language can be difficult to understand; essentially, he is turning his mind to analyze itself instead of blindly accepting data through senses.
Time
By appreciating the qualities of reality and our experience of it, Kant arrives at an important treatment of the concept of time. Time is an important variable in the function of consciousness, because it seems self-explanatory, but the sun seems like it orbits the earth, so why take anything as evidence without proof? Without being able to draw solid deductions about time, Kant turns to treat time transcendentally, and the addition to time to the transcendental elements of reality has a striking effect on the philosophy.
Logical deduction
Kant starts with absolute skepticism and only concludes where logical deduction is appropriate. That does not mean he is not creative in his philosophy, but his creativity stems from an ability to see logical deductions where other people might not notice them. That is a motif that defines Kant's writing, such that any reader, no matter how sophisticated their own philosophy is, will read Kant and learn something from his staggering point of view. He is a genius of logical deduction applying his powers to examining the original philosophical questions of reality.
Transcendental dialectic
A dialectic is an ongoing conversation that keeps a status quo of agreement. Imagine two people having a dispute; when they find common ground, they can work through issues with reference to their agreement, and if one convinces another of a new conclusion, the status quo changes to reflect that. That is what dialectic means. In this book, Kant invents a term called "transcendental dialectic," which means that one is constantly juxtaposing their established ideas with the enormous weight of our limited consciousness. This can be seen as a sophisticated defense of transcendentalism by way of humility (because dialoguing with transcendent ideas has a very humbling effect on one's beliefs).
