This “is” business is tricky. Intransitivity does more damage to identity than “instantiation” because the verbal “engine” of the sentence infers linguistic syntax as a machine, much as Norbert Weiner information theory is prequelled by the second law of thermodynamics that is used to define engine efficiency. Entropy negation in both information technology and mechanical engineering equilibrates a sliding scale sifting the amount of work produced by a steam engine covalent with the clarity of Herman Melville’s sentences. Thus, as intransitivity approximates identity or partial similarity, greater efficiency/clarity results from the momentum turned by verbal transitivity which transforms the “instant” into moment-to-moment differentiation cascading a Newtonian rainbow of calculus.

The equilibration of “is” as the mathematical symbol that separates two halves of an equation, as Butterfield concurs above, may be a different matter altogether indicating the mathematical basis for linguistic behavior is chicken v. egg generated by sapient process. The very notion of “to be” as the verbal form of (=) inversely grounds language as a precursor of, not math itself; but rather as the skeleton key Man has used to ascend to it vide Bronowski’s 1969 equivocation of Roman numerals as a concatenation algebra similar to Chomsky/Rosenbloom 1965 in 'Aspects of the Theory of Syntax': “The European notation for numbers then was still the clumsy Roman style, in which the number is put together from its parts by simple addition [Ascent of Man p. 168].”

I have more on the topic in my compendium, ‘The Linguistics of Math,’ that nobody is interested in reading. Regards to Dr. Abrams.
Rick Goranowski