Can "be" verbs link clauses and/or a clause and a phrase? [closed]

Solution 1:

This is not really about the verb be.

• You are seeing ghosts is what you are seeing.

This sentence is grammatical, though odd enough to draw attention. That's the point. This is an extended Cleft sentence. Clefts of all sorts exist as a sort of syntactic polyploidy to magnify and amplify various parts of sentences.

For instance, the basic sentence all this is derived from is

• You are seeing ghosts.

A Wh-cleft of the basic sentence, focussing on ghosts, produces

• What you are seeing is ghosts.

An It-cleft of the basic sentence, focussing on ghosts, produces

• It is ghosts that you are seeing.

(Clefts can also focus on other constituents, e.g,

• It's you that's seeing ghosts
• What you're doing is seeing ghosts)

In this case, the original sentence is simply re-inserted into its own Wh-cleft:

[You are seeing ghosts] --Wh--> What you are seeing is [you are seeing ghosts].