|Similarity: conformity of one or more - but not all - properties of two or more objects.|
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Numerical equality/Prior: obtained from identity conditions of two statements: "for any f" = (for no x, x ft) and then, only then (for all x, if x ft then x is not identical with x) - therefore, if we abbreviate: "For no x, x ft" to "0xfx" and "For all x, if x ft, then x is not identical with x" to "0" xfx ", then we can say: 0 and 0" "are the same numbers" - these symbols are only fictitious. (as if).
Objects of thought Oxford 1971
Arthur N. Prior
Papers on Time and Tense 2nd Edition Oxford 2003