Is the inversion in the mentioned context idiomatic/grammatical?

Question

But, in either of the above ways is intentionality defined, why not to use the previously mentioned criteria to identify an intentional crime?

In the above sentence "is" is put before the subject. Is this inversion idiomatic/grammatical?

Answer 1

The example needs more context in order to fully understand what the message is. I don't really understand the OP's sentence.

Inversion is used with negative adverbials and expressions in positive sentences. The position of subject and the auxiliary verb is inverted (switched=swapped). For example,

1. Not only does she speak three languages fluently, (but) she writes children's books too.
2. No sooner had she posted her question than someone jumped on her back.
3. She posted her answer. Only then was she able to relax
4. Never was so much owed by so many to so few (Winston Churchill)
5. Hardly had I finished writing my answer when it got downvoted :)

Inversion is useful for adding emphasis, and in (very) formal writing.