In our natural body every part has a necessary sympathy with every other; and all together form, by their harmonious conspiration, a healthy whole.

There is a distinction, but no opposition, between theory and practice. Each to a certain extent supposes the other. Theory is dependent on practice; practice must have preceded theory.

There are two sorts of ignorance: we philosophize to escape ignorance; we start from the one, we repose in the other; they are the goals from which and to which we tend; and the pursuit of knowledge is but a course between two ignorances, as human life is only a traveling from grave to grave.

An instinct is an agent which performs blindly and ignorantly a work of intelligence and knowledge.

Metaphysics, in whatever latitude the term be taken, is a science, or complement of sciences, exclusively occupied with mind.

The pursuit of knowledge is but a course between two ignorances, as human life is itself only a wayfaring from grave to grave.

Truth like a torch, the more 'tis shock, it shines.