The mind takes pleasure in metaphysics because there it finds room; elsewhere, everything is too full. The mind needs a fantastic world in which it can move and wander; it delights less in the objects it meets with than in the space itself. It is thus that children love sand, and water, and all that is fluid or flexible, because they do with it what they will.
 The true science of metaphysics consists not in the rendering abstract that which is sensible, but in rendering sensible that which is abstract; apparent that which is hidden; imaginable, if so it may be, that which is only intelligible; and intelligible finally, that which an ordinary attention fails to seize. [M.A.]
 Whatever may be said, metaphors are as essential to metaphysics as are abstract terms. When metaphors fail you, then, try abstract terms, and when abstract terms are at fault, try metaphor. Grasp the proof, and show it as best you can; there is the whole art and rule of the matter.
 Before an abstract idea can become something of which the mind can form a picture, or even a conception, how much time is needed! How many touches and retouches are wanted to give substance to the shadow!
 A choice of words that presents at first ideas with which you agree, and thus draws you on to admit others with which you would not have agreed, is an argument in disguise. It has the force and the power of a real argument, but is without its harsh, imperious, or repulsive quality.
 As soon as an argument attacks any universal practice or instinct, it may be difficult to refute, but it is certainly delusive. You may not be able to answer it; you must nonetheless be firm in resisting it. The wise man escapes from it by holding to the common opinion.