Criminal psychology is a distinct branch of common psychology and the science of the right to punish. Common psychology teaches the laws of thought or the laws of the natural formation of consciousness; punitive science deals with the juridical genesis of the crime and the legislative norms to prevent and repress it.
From the final agreement of the principles, which regulate the production and evolution of psychic phenomena, with those inherent in the crime phenomenon, criminal psychology is born whose scientific content is in the complex of laws that preside over the psychic formation of the crime phenomenon considered by the dual aspect of evolutionary process and dissolving process.
The treatment of the matter assumed will give an explanation of what we now state. “But how was criminal psychology born and what are its limits of development?
Any progressive phenomenon, that of thought included, is nothing but a distinction made on earlier less distinct phenomena. From the natural formation of the solar system to the highest manifestations of human intelligence, the principle  is constant and is concretized in the growth of precision and coherence with greater integration of the effect produced. that the unity of the phenomenon prevents it from decomposing in the primitive elements.
Therefore, according to Ardigò, “thought is, indeed, multiple and one; for thought, too, is nature, or a natural formation, like all other things.