A metaphor is the application of a word or phrase to something to which it does not literally apply in order to emphasize or indicate a similarity between that to which it would ordinarily apply and that to which it is—nonliterally—being applied.
Conclusion (But)
This cannot be so. i.e., not all uses of language are metaphorical i.e., some uses of language are not metaphorical
Evidence (for)
In order for there to be any nonliteral uses of any words, then some uses of words must be literal.
Evaluate
Whenever we're doing a Main Conclusion question, we prime our brain before reading the paragraph with the two biggest patterns of where they put the conclusion on Main Conclusion: - first sentence - as some sort of rebuttal
This argument did the second: Some extremists claim X. But .. [I disagree]. Here's why.
Conclusion
We just want an equivalent rephrasing of "this cannot be so", so we're looking for something like, "not all uses of language are metaphorical" or "some uses of language are not metaphorical".