individual beings. No monad represents the common universe and its individual parts just as well as the others, but either better or worse. There are as many different degrees of clearness and distinctness as there are monads. Nevertheless certain classes may be distinguished. By distinguishing between clear and obscure perceptions, and in the former class between distinct and confused ones--a perception is clear when it is sufficiently distinguished from others, distinct when its component parts are thus distinguished--Leibnitz reaches three principal grades. Lowest stand the simple or naked monads, which never rise above obscure and unconscious perception and, so to speak, pass their lives in a swoon or sleep. If perception rises into conscious feeling, accompanied by memory, then the monad deserves the name of soul. And if the soul rises to self-consciousness and to reason or the knowledge of universal truth, it is called spirit. Each higher stage comprehends the lower, since even in spirits many perceptions remain obscure and confused. Hence it was an error when the Cartesians made thought or conscious activity--by which, it is true, the spirit is differentiated from the lower beings--to such a degree the essence of spirit that they believed it necessary to deny to it all unconscious perceptions. From perception arises appetition, not as independent activity, but as a modification of perception; it is nothing but the tendency to pass from one perception to another (_l'appetit est la tendance d'une perception à une autre_); impulse is perception in process of becoming. Where the perceptions are conscious and rational appetition rises into will. All monads are self-active or act spontaneously, but only the thinking ones are free. Freedom is the spontaneity of spirits. Freedom does not consist in undetermined choice, but in action without external compulsion according to the laws of one's own being. The monad develops its representations out of itself, from the germs which form its nature. The correspondence of the different pictures of the world, however, is grounded in a divine arrangement, through which the natures of the monads have from the beginning been so adapted to one another that the changes in their states, although they take place in each according to immanent laws and without external influence, follow an exactly parallel course, and the result is the same as though there were a constant mutual interaction. This general idea of a _pre-established harmony_ finds special application in the problem of the interaction between body and soul. Body and soul are like two clocks so excellently constructed that, without needing to be regulated by each other, they show exactly the same time. Over the numberless lesser miracles with which occasionalism burdened the Deity, the one great miracle of the pre-established harmony has an undeniable advantage. As one great miracle it is more worthy of the divine wisdom than the many lesser ones,