Metaphysics has as the proper object of its enquiries three ideas only: God, freedom, and immortality. - Immanuel Kant

unavoidable contradictions, we must not rest satisfied with the mere natural disposition of the mind to metaphysics, that is, with the existence of the faculty of pure reason, whence, indeed, some sort of metaphysical system always arises; but it must be possible to arrive at certainty in regard to the

Habit... makes the endurance of evil easy (which, under the name of patience, is falsely honored as a virtue), because sensations of the same type, when continued without alteration for a long time, draw our attention away from the senses so that we are scarcely conscious of them at all. On the other hand, habit also makes the consciousness and the remembrance of good that has been received more difficult, which then gradually leads to ingratitude (a real vice). [...] Acquired habit deprives good actions of their moral value because it undermines mental freedom and, moreover, it leads to thoughtless repetitions of the same acts (monotony), and thus becomes ridiculous.

All our knowledge falls with the bounds of experience.