Laertius with his Lives of Eminent Philosophers is perhaps the most important source of information that we have on Epicurus, though this information has been implemented by the Herculaneum papyri and in general by other writers and commentators of the Hellenistic era. By not entering in a vivid and contemporary discussion on the Epicurean philosophical system, this article has the aim of exploiting the source of Laertius in order to present and interpret Epicurus's philosophical system as presented in it, thus to unite in a reciprocal way Physics, Ethics and the Canon. Its objective is a clarification of his system by hoping that it can give a precise and simple image of its essence.