naturally conceive it as an essentially stable subject of incessant and evanescent processes. But it is quite arbitrary thus to conceive the _Ego_ as the sole type of substance. Bodies are substances as well as spirits, matter as well as mind. And the permanence of corporeal substances is merely relative. Nevertheless they are really substances. The relative stability of spirit which is immortal, and the relative instability of matter which is corruptible, have nothing to do with the substantiality of either. Both alike are substances, for both alike have that mode of being which consists in their existing in themselves, and not by inhering in other things as accidents do. (_e_) Spencer’s conception of substance as the permanent, unknowable ground of phenomena, implies that substance is one, not manifold, and thus suggests the view of reality known as _Monism_. There is yet another mistaken notion of substance, the notion in which the well known pantheistic philosophy of Spinoza has had its origin. Spinoza appears to have given the ambiguous definition of Descartes—“_Substantia est res quae ita existit, ut nulla alia re indigeat ad existendum_”—an interpretation which narrowed its application down to the Necessary Being; for he defined substance in the following terms: “_Per substantiam intelligo id quod est in se et per se concipitur: hoc est, id cujus conceptus non indiget conceptu alterius rei a quo formari debeat_”. By the ambiguous phrase, that substance “requires no other thing for existing,” Descartes certainly meant to convey what has always been understood by the scholastic expression that substance “exists _in_ itself”. He certainly did not mean that substance is a reality which “exists _of_ itself,” _i.e._ that it is what scholastics mean by _Ens a se_, the Being that has its actuality from its own essence, by virtue of its very nature, and in absolute independence of all other being; for such Being is One alone, the Necessary Being, God Himself, whereas Descartes clearly held and taught the real existence of finite, created substances.(245) Yet Spinoza’s definition of substance is applicable only to such a being that our concept of this being shows forth the actual existence of the latter as absolutely explained and accounted for by reference to the essence of this being itself, and independently of any reference to other being. In other words, it applies only to the Necessary Being. This conception of substance is the starting-point of Spinoza’s pantheistic philosophy.