Thoughts without content are empty, intuitions without concepts are blind. The understanding can intuit nothing, the senses can think nothing. Only through their unison can knowledge arise.

The more a cultivated reason devotes itself to the aim of enjoying life and happiness, the further does man get away from true contentment.

Human freedom is realized in the adoption of humanity as an end in itself, for the one thing that no-one can be compelled to do by another is to adopt a particular end.

He who is cruel to animals becomes hard also in his dealings with men.

— Immanuel Kant

The phenomenality of the empirical world was made fully clear by Kant. Though it is not subject to compelling knowledge, because it cannot be perceived objectively but only by a transcending, nevertheless it imposes itself on every intellect that is capable of transcendence. And then it does not add a new particular knowledge to the knowledges we had before, but effects a shift in our whole consciousness of being. Hence the sudden but enduring light which is kindled in the philosophical approach to the reality of the world. If the light is not kindled, the propositions of philosophy remain unfulfilled and hence fundamentally not understood. It is not only the absolute world systems that are gone. The world is not self-contained and for our knowledge it breaks down into diverse perspectives, because it cannot be reduced to a single principle. The reality of the world as a whole is no object of knowledge.