Abstract: The fundamental purpose of Leo Strauss is defending for an forgotten philosophical life style, and the question of first importance of this purpose is answering why the philosophical life style is worth defending. For Strauss and his classical philosophy, philosophy is a life style which is continuously searching the truth and inquiring the whole. It is an inexhaustible strive using the episteme of the whole substitute for the opinion of the whole. The philosopher follows the guiding of reason, opens to the whole in his searching life, and merges into the single whole. This life fulfills the highest level of self-sufficiency in a possible range, so it is the happiest life. This is the fundamental cause why the philosophical life is worth defending