Philosophy Lexicon of Arguments

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Cantor, G.
 
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Real Numbers Thiel I 197
Real numbers/Cantor/Thiel:
Eugen D├╝hring 1861: Every amount, which is thought of as something finished, is a definite one.
Real numbers/CantorVsD├╝hring/Thiel: an uncountable whole is something finished (even something "actual"), i.e. a certain number.
Cantor: no countable list of dual sequences can contain all the dual sequences.
Rather, from the outset the set of real numbers or the set of dual sequences is considered given, and the assumption that this set is countable, is then depicted as refuted by the diagonal construction.
The unquestionable assumption of the "set" of all real numbers or dual sequences corresponds entirely to the interpretation of the conducted proof which, according to the classical view, provides more than the purely negative result of non-countability:
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I 198
Since the already accepted set of all real numbers must have a powerfulness, that is infinite, but not equal to the basic numbers. So there must be a greater powerfulness. Corresponding to the notion of the determinateness of all amounts or powerfulnesses, it also receives a name, e.g. "c".
Thus, we also seem to have a "transfinite" cardinal number: the powerfulness of the continuum, which is greater than the powerfulness of the set of the basic numbers. Cantor has positively attempted to prove a whole more realm of the over-countable.
ConstructivismVs: there is no set of real numbers since a statement form representing this set is missing.
In addition, with the dual sequences, this means an impermissible advance on construction means, which are not yet available.
The special construction instruction for dual sequences would even be contradictory because it demands to construct a dual sequence that is different from all dual sequences. (So also different from itself).
(s) E.g. it is, however, easy to construct with the numbers 2 and 3 a number different from these: "2 + 3 = 5".
Vs: sure, but that does not correspond to the requirement to construct a number that is different from all natural numbers. But this can also be done: E.g. 2/3 is different from all natural numbers.

T I
Chr. Thiel
Philosophie und Mathematik Darmstadt 1995


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Ed. Martin Schulz, access date 2017-04-27