5.53
Identity of the object I express by identity of the sign and not by means of a sign of identity. Difference of the objects by difference of the signs.
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- 5.531 I write therefore not “f(a,b).a=b” but “f(a,a)” (or “f(b,b)”). And not “f(a,b).~a=b”, but “f(a,b)”.
- 5.532 And analogously: not “(∃x,y).f(x,y).x=y”, but “(∃x).f(x,x)”; and not “(∃x,y).f(x,y).~x=y”, but…
- 5.533 The identity sign is therefore not an essential constituent of logical notation.
- 5.534 And we see that the apparent propositions like: “a=a”, “a=b.b=c.⊃a=c”, “(x).x=x”. “(∃x).x=a”, etc.…
- 5.535 So all problems disappear which are connected with such pseudo-propositions. This is the place to…