TWO:It is well known that Spinoza draws a sharp line of demarcation between the two attributes of Extension and Thought, which, with him, correspond to what are usually called body and mind. Neither attribute can act on the other. Mind receives no impressions from body, nor does body receive any impulses from mind. This proposition follows by rigorous logical necessity from the Platonic principle that mind is independent of body, combined with the Stoic principle that nothing but body can act on body, generalised into the wider principle that interaction implies homogeneity of nature. According to some critics, Spinozas teaching on this point constitutes a fatal flaw in his philosophy. How, it is asked, can we know that there is any such thing as body (or extension) if body cannot be perceived,for perceived it certainly cannot be without acting on our minds? The idea of infinite substance suggests a way out of the408 difficulty. I find in myself, Spinoza might say, the idea of extension. In fact, my mind is nothing but the idea of extension, or the idea of that idea, and so on through as many self-reflections as you please. At the same time, mind, or thought, is not itself extended. Descartes and the Platonists before him have proved thus much. Consequently I can conceive extension as existing independently of myself, and, more generally, of all thought. But how can I be sure that it actually does so exist? In this wise. An examination of thought leads me to the notion of something in which it residesa substance whose attribute it is. But having once conceived such a substance, I cannot limit it to a single attribute, nor to two, nor to any finite number. Limitation implies a boundary, and there can be no boundary assigned to existence, for existence by its very definition includes everything that is. Accordingly, whatever can be conceived, in other words whatever can be thought without involving a contradiction,an important reservation which I beg you to observe,must necessarily exist. Now extension involves no contradiction, therefore it exists,exists, that is to say, as an attribute of the infinite substance. And, by parity of reasoning, there must be an idea of extension; for this also can exist without involving a contradiction, as the simplest introspection suffices to show. You ask me why then I do not believe in gorgons and chimaeras. I answer that since, in point of fact, they do not exist, I presume that their notion involves a contradiction, although my knowledge of natural law is not sufficiently extended to show me where the contradiction lies. But perhaps science will some day be able to point out in every instance of a non-existing thing, where the contradiction lies, no less surely than it can now be pointed out in the case of impossible geometrical figures. In short, while other people travel straight from their sensations to an external world, Spinoza travels round to it by the idea of an infinite substance.564
THREE:I started on my return journey to The Netherlands sick to death. The consequences of lying on that wet floor made themselves badly felt, and besides being quite stiff and chilly, my interior was badly out of order.
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THREE:Finally, while the attempt to attain extreme accuracy of definition was leading to the destruction of all thought and all reality within the Socratic school, the dialectic method had been taken up and parodied in a very coarse style by a class of persons called Eristics. These men had, to some extent, usurped the place of the elder Sophists as paid instructors of youth; but their only accomplishment was to upset every possible assertion by a series of verbal juggles. One of their favourite paradoxes was to deny the reality of falsehood on the Parmenidean principle that nothing cannot exist. Plato satirises their method in the Euthydmus, and makes a much more serious attempt to meet it in the Sophist; two Dialogues which seem to have been composed not far from one another.156 The Sophist effects a considerable simplification in the ideal theory by resolving negation into difference, and altogether omitting the notions of unity and plurality,perhaps as a result of the investiga265tions contained in the Parmenides, another dialogue belonging to the same group, where the couple referred to are analysed with great minuteness, and are shown to be infected with numerous self-contradictions. The remaining five ideas of Existence, Sameness, Difference, Rest, and Motion, are allowed to stand; but the fact of their inseparable connexion is brought out with great force and clearness. The enquiry is one of considerable interest, including, as it does, the earliest known analysis of predication, and forming an indispensable link in the transition from Platonic to Aristotelian logicthat is to say, from the theory of definition and classification to the theory of syllogism.
