Existence--the existence of material realities--is given us at first by sense; sense attains the object as existing; that is to say, in the real and existing influence by which it acts upon our sensorial organs. This is why the pattern of all true knowledge is the intuition of the thing that I see, and that sheds its light upon me. Sense attains existence in act without itself knowing that it is existence. Sense delivers existence to the intellect; it gives the intellect an intelligible treasure which sense does not know to be intelligible, and which the intellect, for its part, knows and calls by its name, which is being.
Jacques Maritain, Existence and the Existent, p. 21.