## Philosophy Lexicon of Arguments | |||

Author | Item | Excerpt | Meta data |
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Hilbert, D. Books on Amazon |
Infinity Axiom | Berka I 122 Definition number/logical form/extended function calculus/Hilbert: also the general number concept can be formulated logically: If a predicate-predicate φ (F) should be a number, then φ must satisfy the following conditions: 1. For two equal predicates F and G, φ must be true for both or none of them. 2. If two predicates F and G are not equal in number, φ can only be true for one of the two predicates F and G. Logical form: (F)(G){(φ(F) & φ(G) > Glz (F,G) & [φ(F) & Glz (F,G) > φ(G)]}. The entire expression represents a property of φ. If we designate it with Z (φ), then we can say: A number is a predicate-predicate φ that has the property Z (φ). Problem/> Infinity axiom/Hilbert: a problem occurs when we ask for the conditions under which two predicate-predicates φ and ψ define the same number with the properties Z (φ) and Z (ψ). Infinity axiom/Equal numbers/Hilbert: the condition for equal numbers or for the fact that two predicate-predicates φ and ψ define the same number is that, that φ(P) and ψ(P) are true for the same predicates P and false for the same predicates. So that the relationship arises: (P)(φ(P) ↔ ψ(P)) I 122 Problem: when the object area is finite, all the numbers are made equal which are higher than the number of objects in the individual area. For example, if a number is e.g. smaller than 10 to the power of 60 and if we take φ and ψ the predicates which define the numbers 10 to the power of 60+1 and 10 high 60 + 1, then both φ and ψ do not apply to any predicate P. The relation (P)(φ(P) ↔ ψ(P)) Is thus satisfied for φ and ψ, that is, φ and ψ would represent the same number. Solution/Hilbert: infinity axiom: one must presuppose the individual domain as infinite. A logical proof of the existence of an infinite totality is, of course, dispensed with. |
Brk I K. Berka/L. Kreiser Logik Texte Berlin 1983 |

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Ed. Martin Schulz, access date 2017-03-27