Karl Popper's aim in Logik der Forschung is to consider the method of investigation used by the empirical sciences. Many people would say that their procedure is marked by the use of induction, and accordingly that the logic of scientific investigation is the logical analysis of induction. But Popper disagrees. Scientific procedure consists of two steps, an hypothesis is formed, and then it is tested. Logic is only concerned with questions of validity, and thus is only concerned with the second of these steps. But every method of testing validity is deductive, and thus the logic of scientific investigation is the study of deduction as used by the empirical sciences.