In his recent UCLA Lectures, Chomsky makes the following two suggestive remarks which seem to be contradictory:

. . . [I]magine the simplest case where you have a lexicon of one element and we have the operation internal Merge. [. . . ] You have one element: let’s just give it the name

p24zero(0). We internally merge zero with itself. That gives us the set {0, 0}, which is just the set zero. Okay, we’ve now constructed a new element, the set zero, which we callone.

We want to say that [X], the workspace which is a set containing X is distinct from X.

p37

[X] ≠ X

We don’t want to identify a singleton set with its member. If we did, the workspace itself would be accessible to MERGE. However, in the case of the elements produced by MERGE, we want to say the opposite.

{X} = X

We want to identify singleton sets with their members.

So in the case of arithmetic, a singleton set ({0}, *one*) is distinct from its member (0), but the two are identical in the case of language. This is either a contradiction—in which case we need to eliminate one of the statements—or its an equivocation—in which case we need to find and understand the source of the error. The former option would be expedient, but the latter is more interesting. So, I’ll go with the latter.

The source of the equivocation, in my estimation, is the notion of identity—Chomsky’s remarks become consistent when we take him to be using different measures of identity and, in order to understand these distinctions, we need to dust off a rarely used dichotomy—form vs substance.

This dichotomy is perhaps best known to syntacticians due to Chomsky’s distinction between “formal universals” and “substantive universals” in *Aspects*, where formal universals were constraints on the types of grammatical rules in the grammar and substantive universal were constraints on the types of grammatical objects in the grammar. Now, depending on what aspect of grammar or cognition we are concerned with, the terms “form” and “substance” will pick out different notions and relations, but since we’re dealing with syntax here we can say that “form” picks out purely structural notions and relations, such as are derived by merge, while substance picks out everything else.

By extension, then, two expressions are formally identical if they are derived by the same sequences of applications of merge. This is a rather expansive notion. Suppose we derived a structure from an arbitrary array A of symbols, any structure whose derivation can be expressed by swapping the symbols in A for distinct symbols will be formally identical to the original structure. So, “The sincerity frightened the boy.” and “*The boy frightened the sincerity” would be formally identical, but, obviously, substantively distinct.

Substantive identity, though is more complex. If substance picks out everything except form, then it would pick out everything to do with the pronunciation and meaning of an expression. So, from the pronunciation side, a structurally ambiguous expression is a set of (partially) substantively identical but formally distinct sentences, as are paraphrases on the meaning side.

Turning back to the topic at hand, the distinction between a singleton set and its member is purely formal, and therein lies the resolution of the apparent contradiction. Arithmetic is purely formal, so it traffics in formal identity/distinctness. Note that Chomsky doesn’t suggest that zero is a particular object—it could be any object. Linguistic expressions, on the other hand, have form *and* substance. So a singleton set {LI} and its member LI are formally distinct but, since they would mean and be pronounced the same, are substantively identical.

It follows from this, I believe, that the narrow faculty of language, if it is also responsible for our faculty of arithmetic, must be purely formal—constructing expressions with no regard for their content. So, the application of merge cannot be contingent on the contents of its input, nor could an operation like Agree, which is sensitive to substance of an expression, be part of that same faculty. These conclusions, incidentally, can also be drawn from the Strong Minimalist Thesis

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