§ 10. We can intuit things "a priori" only through the mere form of sensuous intuition. In so doing, we can only know objects as they appear to us, not as they are in themselves, apart from our sensations. Mathematics is not an analysis of concepts. Mathematical concepts are constructed from a synthesis of intuitions. Geometry is based on the pure intuition of space. The arithmetical concept of number is constructed from the successive addition of units in time. Pure mechanics uses time to construct motion. Space and time are pure "a priori" intuitions. They are the mere forms of our sensations and exist in us prior to all of our intuitions of objects. Space and time are "a priori" knowledge of a sensed object as it appears to an observer.