Being a short manual offers the advantage of quick sketch, in which the essential features and meaning of the set are strongly seconded to dispense with the multiplicity of details. It is not really a reference work (this is provided by the History of Philosophy, in two volumes by the same author), but serves as initiation into the matter. The mission of the historian is not limited to the simple exposition of philosophical ideas, but also should be invited from their special focus, to relive the historic event and to rethink the problems and doctrines, contributing to the formation of general philosophical reader. The aim pursued by the author is primarily initiated in the spirit of philosophy, offering a clear view of the historical process that has led to approach philosophical problems and has led meditation on them.