123. If you maintain that extension is not the essence of bodies, but an attribute or modification of bodies, whether a determination founded on their essence or an accidental determination, and pretend that this modification or attribute may belong to the only substance, we ask you whether this substance in itself abstracted from extension is simple or composite. If composite, it implies multiplicity, and Spinosa coincides with the common opinion of a corporeal world, composed of many parts, one of which will have no more right than another to be the true substance. For then there would not be a single substance, but one composed of many; and the corporeal universe cannot be called a substance except in the sense in which it is commonly called one, that is, not taking the oneness in a strict sense, but inasmuch as all its parts are connected together, and disposed in a certain order to conspire to the same end. If the substance, the subject of extension is simple, the result will be a simple substance determined or modified by extension, a simple extended substance, which is a contradiction. A thing cannot be conceived as a modification of another unless it is modified by it; this is what the words express. A modification modifies, giving to the thing modified the form of the modification, applying itself to the thing modified. Extension cannot modify except by making the thing modified extended; and to be extended, and to have extension, are absolutely identical expressions. Therefore it is repugnant for a simple substance to have extension for one of its modifications; therefore Spinosa's system is absurd. CHAPTER XVII. PANTHEISM EXAMINED IN THE ORDER OF INTERNAL FACTS.