of knowledge and of opinion cannot be the same.

Then if being is the subject-matter of knowledge, something else must be the subject-matter of opinion?

Yes, something else.

Well then, is not-being the subject-matter of opinion? or, rather, how can there be an opinion at all about not-being? Reflect: when a man has an opinion, has he not an opinion about something? Can he have an opinion which is an opinion about nothing?

Impossible.

He who has an opinion has an opinion about some one thing?

Yes.

And not-being is not one thing but, properly speaking, nothing?

True.