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The notions themselves may not necessarily need to be stated; Susan Haack (1978) writes, "A set of axioms is sometimes said to give an implicit definition of its primitive terms." [7] Euclidean geometry: Under Hilbert's axiom system the primitive notions are point, line, plane, congruence, betweenness , and incidence.
Stating definitions and propositions in a way such that each new term can be formally eliminated by the priorly introduced terms requires primitive notions (axioms) to avoid infinite regress. This way of doing mathematics is called the axiomatic method. [4] A common attitude towards the axiomatic method is logicism.
Hilbert's axiom system is constructed with six primitive notions: three primitive terms: [5] point; line; plane; and three primitive relations: [6] Betweenness, a ternary relation linking points; Lies on (Containment), three binary relations, one linking points and straight lines, one linking points and planes, and one linking straight lines ...
Peano's 1889 work on geometry, largely a translation of Pasch's treatise into the notation of symbolic logic (which Peano invented), uses the primitive notions of point and betweeness. [28] Peano breaks the empirical tie in the choice of primitive notions and axioms that Pasch required.
Other choice axioms weaker than axiom of choice include the Boolean prime ideal theorem and the axiom of uniformization. The former is equivalent in ZF to Tarski 's 1930 ultrafilter lemma : every filter is a subset of some ultrafilter .
The axioms in order below are expressed in a mixture of first order logic and high-level abbreviations. Axioms 1–8 form ZF, while the axiom 9 turns ZF into ZFC. Following Kunen (1980), we use the equivalent well-ordering theorem in place of the axiom of choice for axiom 9. All formulations of ZFC imply that at least one set exists.
The only primitive relations are "betweenness" and "congruence" among points. Tarski's axiomatization is shorter than its rivals, in a sense Tarski and Givant (1999) make explicit. It is more concise than Pieri's because Pieri had only two primitive notions while Tarski introduced three: point, betweenness, and congruence.
The primitive notions of his theory were function and argument. Using these notions, he defined class and set. [1] Paul Bernays reformulated von Neumann's theory by taking class and set as primitive notions. [2] Kurt Gödel simplified Bernays' theory for his relative consistency proof of the axiom of choice and the generalized continuum ...