§ 149. The Eleatic reasons somewhat as follows. The philosopher seeks to know what is. The object of his knowledge will then contain as its primary and essential predicate, that of being. It is a step further to _define_ being in terms of this essential predicate. Parmenides thinks of being as a power or strength, a positive self-maintenance to which all affirmations refer. The remainder of the Eleatic philosophy is the analysis of this concept and the proof of its implications. Being must persist through all change, and span all chasms. Before being there can be only nothing, which is the same as to say that so far as being is concerned there is no before. Similarly there can be no after or beyond. There can be no motion, change, or division of being, because being will be in all parts of every division, and in all stages of every process. Hence being is "uncreated and indestructible, alone, complete, immovable, and without end." The argument turns upon the application to being as a whole of the meaning and the implications of _only being_. Being is the affirmative or positive. From that _alone_, one can derive only such properties as eternity or unity. For generation and decay and plurality may belong to that which is _also_ affirmative and positive, but not to that which is affirmative and positive _only_. The Eleatic philosophy is due, then, to the determination to derive the whole of reality from the bare necessity of being, to cut down reality to what flows entirely from the assertion of its only known necessary aspect, that of being. We meet here in its simplest form a persistent rationalistic motive, the attempt to derive the universe from the isolation and analysis of its most universal character. As in the case of every well-defined philosophy, this motive is always attended by a "besetting" problem. Here it is the accounting for what, empirically at least, is alien to that universal character. And this difficulty is emphasized rather than resolved by Parmenides in his designation of a limbo of opinion, "in which is no true belief at all," to which the manifold of common experience with all its irrelevancies can be relegated. [Sidenote: Spinoza's Conception of Substance.]