According to Koyré, it was not the experimental or empirical nature of Galileo's and Newton's discoveries that carried the Scientific Revolution of the 16th and 17th centuries, but a shift in perspective, a change in theoretical outlook toward the world. Koyré strongly criticized what he called the "positivist" notion that science should only discover given phenomena, the relations between them and certain laws that would help to describe or predict them. To Koyré science was, at its heart, theory: an aspiration to know the truth of the world, of uncovering the essential structures from which phenomena, and the basic laws that relate them, spring.