5,953
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Tractatus Logico-Philosophicus (English): Difference between revisions
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5.5301 That identity is not a relation between objects is obvious. This becomes very clear if, for example, one considers the proposition "(''x'') : ''f x'' . ⊃ . ''x'' = ''a''" What this proposition says is simply that ''only'' ''a'' satisfies the function ''f'', and not that only such things satisfy the function ''f'' which have a certain relation to ''a''. | 5.5301 That identity is not a relation between objects is obvious. This becomes very clear if, for example, one considers the proposition "(''x'') : ''f x'' . ⊃ . ''x'' = ''a''" What this proposition says is simply that ''only'' ''a'' satisfies the function ''f'', and not that only such things satisfy the function ''f'' which have a certain relation to ''a''. | ||
One could of course say that in fact ''only'' | One could of course say that in fact ''only'' ''a'' has this relation to ''a'' but in order to express this we should need the sign of identity itself. | ||
5.5302 Russell's definition of "=" won't do; because according to it one cannot say that two objects have all their properties in common. (Even if this proposition is never true, it is nevertheless ''significant''.) | 5.5302 Russell's definition of "=" won't do; because according to it one cannot say that two objects have all their properties in common. (Even if this proposition is never true, it is nevertheless ''significant''.) | ||