text: Therefore, gird yourself about with philosophy, an impregnable wall. Though it be assaulted by many engines, Fortune can find no passage into it. The soul stands on unassailable ground, if it has abandoned external things; it is independent in its own fortress; and every weapon that is hurled falls short of the mark. Fortune has not the long reach with which we credit her; she can seize none except him that clings to her. Let us then recoil from her as far as we are able. This will be possible for us only through knowledge of self and of the world of Nature. The soul should know whither it is going and whence it came, what is good for it and what is evil, what it seeks and what it avoids, and what is that Reason which distinguishes between the desirable and the undesirable, and thereby tames the madness of our desires and calms the violence of our fears.