The present work is the result of a struggle towards the comprehension of what is so vaguely named human nature. For modern philosophy in general, Man is defined by its capacity of giving meaning to things and therefore acknowledging and organizing the world - or, in other words, by its intellectual faculty (reason) - which make this species differ from all others among nature. Our object is the conception of such human nature as shaped by the seventeenth century philosophy, built over an anthropocentric and rationalist perspective. We confront this conception to the one of Baruch Spinoza, which allows us to enlighten the conditions of individuation, shifting from reason to affects as the elements mainly responsible for such process. The use of Spinoza s philosophy is focused at the Ethics, especially Parts I and IV, in which Spinoza builds his ontology and his theory of affects. Thus, our intention is to compare these comprehensions of human nature which correspondingly imply different ontological theories.