Immanuel Kant 
Critique of Pure Reason [PDF ebook] 

The Critique of Pure Reason is one of the seminal texts of Western philosophy, and the first of Kant’s three Critiques. In it he takes up Hume’s argument that cause and effect cannot be experienced by the senses. Hume argued that we experience events one after the other, but not that one event is caused by the preceding event. Kant argues that synthetic, rather than analytic thinking is needed, and addresses the problem of thinking synthetically without relying on the empirical method.