 Locke (see the entry on  Locke)  took from the Aristotelian tradition the idea that Euclidean geometry and rational theology are the exemplars of scientific knowledge, but sought to ground his philosophy in intuitive, demonstrative, and sensitive kinds of knowledge. Intuitive knowledge is what is grasped immediately; demonstrative knowledge avails itself of the intermediate steps of a proof, as in geometry. Both these forms of knowledge are certain. Sensitive knowledge is not certain: it is what we learn through our senses, it presents effects but not causes, it is at best partial and may be deceptive. Space can be thought of as composed of all (actual and possible) positions of objects; pure space is space with all solid bodies removed, and distance the primitive concept we use to discuss the separation between bodies.