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intersubstitutability
intersubstitutability n. 
/ˌɪntəsʌbstᵻtʃuːtəˈbɪlᵻti/,
Brit. /ˌɪntəsʌbstᵻtjuːtəˈbɪlᵻti/
, /ˌɪntəsʌbstᵻtjuːtəˈbɪlᵻti//ˌɪntəsʌbstᵻtʃuːtəˈbɪlᵻti/U.S. /ˌɪn(t)ərˌsəbstəˌt(j)udəˈbɪlᵻdi/
/ˌɪn(t)ərˌsəbstəˌt(j)udəˈbɪlᵻdi/Π
1954 I. M. Copi Symbolic Logic vii. 224 Of the list of elementary valid argument forms..the last ten were equivalences whose intersubstitutability was assumed.
1957 P. Geach Mental Acts 90 We cannot define synonymy as a supreme degree of equivalence, intersubstitutability salva veritate in all contexts.
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