Therefore, one radically is against to Plato, the scholastic philosophers and mainly to Discardings, when affirming that intuitive ideas or general principles do not exist or a priori. Locke says that the mind fills of symbols and from all the ideas of the experience, on which our knowledge is based all and of which, in last instance, all the is derived. Aside from this philosophical inheritance, the field that has contributed more to the development of scientific psychology has been the physiology, that is to say, the study of the functions of the diverse organs and systems of the human body. The German physiologist Mller (1938) tried to relate the sensorial experience to the activities of the nervous system and the physical surroundings of the organisms, but the first authentic representatives of experimental psychology were the German physicist Gustav Theodor Fechner and the physiologist, also German, Wilhelm Wundt. Both are considered the parents of present scientific psychology.
Fechner developed experimental methods to measure the intensity of the sensations and to relate it to the one of the physical stimuli caused that them, establishing the law that takes its name and that is, still today, one of the basic principles of perception. Wundt, that in 1879 founded the first laboratory of experimental psychology on the German city of Leipzig, formed to students of the entire world in the new science. Freud (1900) elaborated the method of investigation and treatment known like psychoanalysis. In its works, Freud drew attention on the unconscious pulsiones (instincts) and processes that determine the human behavior. In Mexico, like anywhere in the world, it can be spoken of an historical stage previous to the sprouting of psychology like science, in which the study of subjects psychological in the amplest sense of the term is approached, that is to say, bound to medical and philosophical problems, from long before century XIX.
