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Signs: as long as E.g. the plus sign is used only between integers ("a + b"), it only needs to be explained for this purpose. If other objects are to be linked, E.g. "sun" with something else, the plus sign must be redefined.
Frege: Sign: Deputy.
Numeral/Frege: E.g. "2" - saturated - in contrast: functional character - E.g. "sin" (sine) unsaturated.
Sign/Frege: are the requirements for conceptual thinking - they no longer refer to the individual thing, but to what several things have in common.
Sign/FregeVsFormalism: empty signs are only black spots on paper - their use would be a logical error. - Empty signs do not solve any task E.g. x + b = c: if b>c, there is no natural number x that can be inserted - nor to accept the difference (c-b) as an artificial new sign. Sign/Frege: and where a solution is possible, the sign is not the solution, but the meaning of the sign.
FregeVsFormalism: only gives instructions for definitions - no definitions themselves.
E.g. Number i: the meaning of "total" must be re-explained. - FregeVsHilbert: it is not enough just to call for a sense.
Die Grundlagen der Arithmetik Stuttgart 1987
Funktion, Begriff, Bedeutung Göttingen 1994
Logische Untersuchungen Göttingen 1993