§ 150. The Eleatic philosophy, enriched and supplemented, appears many centuries later in the rigorous rationalism of Spinoza.[311:4] With Spinoza philosophy is a demonstration of necessities after the manner of geometry. Reality is to be set forth in theorems derived from fundamental axioms and definitions. As in the case of Parmenides, these necessities are the implications of the very problem of being. The philosopher's problem is made to solve itself. But for Spinoza that problem is more definite and more pregnant. The problematic being must not only be, but must be _sufficient to itself_. What the philosopher seeks to know is primarily an intrinsic entity. Its nature must be independent of other natures, and my knowledge of it independent of my knowledge of anything else. Reality is something which need not be sought further. So construed, being is in Spinoza's philosophy termed _substance_. It will be seen that to define substance is to affirm the existence of it, for substance is so defined as to embody the very qualification for existence. Whatever exists exists under the form of substance, as that "which is in itself, and is conceived through itself: in other words, that of which a conception can be formed independently of any other conception."[312:5] [Sidenote: Spinoza's Proof of God, the Infinite Substance. The Modes and the Attributes.] § 151. There remains but one further fundamental thesis for the establishment of the Spinozistic philosophy, the thesis which maintains the exclusive existence of the one "absolutely infinite being," or God. The exclusive existence of God follows from his existence, because of the exhaustiveness of his nature. His is the nature "consisting in infinite attributes, of which each expresses eternal and infinite essentiality." He will contain all meaning, and all possible meaning, within his fixed and necessary constitution. It is evident that if such a God exist, nothing can fall outside of him. One such substance must be the only substance. But upon what grounds are we to assert God's existence? To proceed further with Spinoza's philosophy we must introduce two terms which are scarcely less fundamental in his system than that of substance. The one of these is "attribute," by which he means _kind_ or general property; the other is "mode," by which he means _case_ or individual thing. Spinoza's proof of God consists in showing that no single mode, single attribute, or finite group of modes or attributes, can be a substance; but only an infinite system of all modes of all attributes. Translated into common speech this means that neither kinds nor cases, nor special groups of either, can stand alone and be of themselves, but only the unity of all possible cases of all possible kinds.