Soil science is strictly connected to other branches of science like mathematics, physics, chemistry, and biology, and soil scientists have to make reference to them as a whole when investigating the soil system. Any of the science branches mentioned above raises specific philosophical issues like those linked to scientific method or to the concept of explanation, which is not univocal for all sciences. The scientific method is often represented as a procedure that takes to the explanation of facts starting from observation through deductive and inductive thinking. An epistemological approach to this issue puts in evidence the importance of another type of inference, different from those just mentioned above: the abductive inference. Which roles are played, for soil scientists, by hypothesis and which are the inferences leading to their formulation? Which are the conditions to be respected for a hypothesis to become a scientific hypothesis? In this paper we have followed the history and evolution of scientific method and its more important milestones from the ancient to the modern age, underlining, where possible, peculiar characteristics of scientific investigation. The main objective of the work was to put in evidence, through a simple historical examination of some of the more important discoveries of soil science, the logical procedures leading to the formulation of theories or discovery in general.