Hierarchy and metaphysics
Kant sees the world in terms of invisible systems that are stacked upon one another in a matrix of systems. The physical universe is a manifestation of matter obeying these systems, so that the laws of nature could be viewed as a metaphysical reality onto which reality is pinned. Those laws can be abstracted like a function in math could be integrated, for the discovery of more basic principles. Kant's theories apply this hierarchy to the issues of philosophy, including morality, language, science, and the meaning of life.
Rationalism as an incomplete system
Kant argues that Rationalism is an incomplete system, and he depicts this through imagery. There is no way to literally perceive what is imperceptible to the human mind, but through imaginary imagery, Kant explores the kinds of data that humans can't understand. For instance, there is no way to conceive what might lie beyond the grasp of the human mind. This theory came a long time before the absolute mysteries of quantum physics, but quantum conundrums like superposition would be a perfect example of when Rationalism is not scientific enough, because it constrains the universe to behave in ways that in reality, the universe does not. He demonstrates that absolute Rationalism is a human being demanding that the universe be less mysterious than it is.
Imperatives and goodness
Kant ruffles a lot of feathers in the philosophical community when he argues that there are unignorable moral principles or imperatives that are obvious to humans throughout time. By observing the human animal scientifically, he draws the conclusion that humans share a moral compass that calculates moral conundrums through a hierarchy of goodness. He fosters this view and explains how those imperatives might operate, offering moral puzzles and solving them according to his own morality.
Mystery and transcendentalism
The argument could be made that Kant is offering a philosophy of religious mysticism and transcendentalism to his reader. Perhaps this is unintentional, but through time, the philosophical community has often noticed this mysticism in his writing. It is in the imagery of his philosophy, because when he arrives at philosophical mysteries like the mystery of time, the mystery of the manifest universe, the mystery of human consciousness in a moral framework—he doesn't offer solutions to those problems; he merely observes that they are technically beyond the capacities of the human mind. He denies religion a place in his philosophy by refusing to speculate, and this objectivity leads to a kind of philosophical transcendentalism.
