“If we wish to express our ideas in terms of the concepts synthetic and analytic, we would have to point out that these concepts are applicable only to sentences that can be either true of false, and not to definitions. The mathematical axioms are therefore neither synthetic nor analytic, but definitions. …Hence the question of whether axioms are a priori becomes pointless since they are arbitrary.”
The Philosophy of Space and Time (1928, tr. 1957)
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Hans Reichenbach 41
American philosopher 1891–1953Related quotes

Source: 1930s, Principles of topological psychology, 1936, p. viii.

Instead we shall speak of the normative function of the thinking process, which can guide the pictorial elements of thinking into any logically permissible structure.
The Philosophy of Space and Time (1928, tr. 1957)

“Every definition implies an axiom, since it asserts the existence of the object defined.”
Part II. Ch. 2 : Mathematical Definitions and Education, p. 131
Science and Method (1908)
Context: Every definition implies an axiom, since it asserts the existence of the object defined. The definition then will not be justified, from the purely logical point of view, until we have proved that it involves no contradiction either in its terms or with the truths previously admitted.

As quoted in Carl Friedrich Gauss: Titan of Science (1955) by Guy Waldo Dunnington. p. 362
Geometry as a Branch of Physics (1949)

But generally the positivistic scheme taken from mathematical logic is too narrow in a description of nature which necessarily uses words and concepts that are only vaguely defined.
Physics and Philosophy (1958)

Source: "The Latest Attack on Metaphysics" (1937), p. 146.

Can scientific methods prove the existence of God? https://www.americamagazine.org/content/all-things/god-and-science-qa-robert-spitzer-sj (December 29, 2015)