The lesson that there are limits to our knowledge is an old lesson, but it has to be taught again and again. It was taught by Buddha, it was taught by Socrates, and it was taught for the last time in the most powerful manner by Kant. Philosophy has been called the knowledge of our knowledge; it might be called more truly the knowledge of our ignorance, or, to adopt the more moderate language of Kant, the knowledge of the limits of our knowledge.

Last Essays.

Metaphysical truth is wider than physical truth, and the new discoveries of physical observers, if they are to be more than merely contingent truths, must find their appointed place and natural refuge within the immovable limits traced by the metaphysician.... It is only after having mastered the principles of metaphysics that the student of nature can begin his work in the right spirit, knowing the horizon of human knowledge, and guided by principles as unchangeable as the pole star.

Last Essays.

There is no subject in the whole realm of human knowledge that cannot be rendered clear and intelligible, if we ourselves have perfectly mastered it.

Chips.

The bridge of thoughts and sighs that spans the whole history of the Aryan world has its first arch in the Veda, its last in Kant's Critique of Pure Reason. In the Veda we watch the first unfolding of the human mind as we can watch it nowhere else. Life seems simple, natural, childlike.... What is beneath, and above, and beyond this life is dimly perceived, and expressed in a thousand words and ways, all mere stammerings, all aiming to express what cannot be expressed, yet all full of a belief in the real presence of the Divine in Nature, of the Infinite in the Finite.... While in the Veda we may study the childhood, we may study in Kant's Critique the perfect manhood of the Aryan mind. It has passed through many phases, and every one of them ... has left its mark. It is no longer dogmatical, no longer sceptical, least of all is it positive.... It stands before us conscious of its weakness and its strength, modest yet brave. It knows what the old idols of its childhood and youth were made of. It does not break them, it only tries to understand them, but it places above them the Ideals of Reason—no longer tangible—not even within the reach of the understanding—but real—bright and heavenly stars to guide us even in the darkest night.

Last Essays.

All knowledge, in order to be knowledge, must pass through two gates, and two gates only: the gate of the senses and the gate of reason. Religious knowledge also, whether true or false, must have passed through these two gates. At these two gates, therefore, we take our stand. Whatever claims to have entered in by any other gate, whether that gate is called primeval revelation or religious instinct, must be rejected as contraband of thought; and whatever claims to have entered by the gate of reason, without having first passed through the gate of the senses, must equally be rejected, as without sufficient warrant, or ordered at least to go back to the first gate, in order to produce there its full credentials.

Hibbert Lectures.