The Logic of Scientific Discovery
The Logic of Scientific Discovery is a 1959 book by Karl Popper. Sir Peter Medawar called it "One of the most important documents of the twentieth century." In it, Popper argued that science proceeds by falsification; that is, no number of experiments can ever prove a theory, but a single experiment can disprove one. Thus, falsifiability is an essential characteristic of any scientific theory.
The text is currently in print by Routledge publishers (ISBN 0415278449).