reason

[svartnik]

Hello

That is the reason that he did not call.

My question is: what is the antecedent of that in the sentence?

What is the noun clause hinges on?

thanks

[Niall]

As is evident, this independant clasue does not rely on a noun.

We call this use of "that" a restrictive clause. Restrictive causes do infact often rely on nouns, but not all the time. Here, "that" is simply being used to single out a phenomenon, rather than a noun.