If you work for a while in the belief that an object with certain properties should exist, and eventually learn otherwise, then you will have discovered that the set of such objects is empty. I just now gave an MO answer of this type! mathoverflow.net/a/376107/2926

@adamC If you want to delete, there's a button for that. If you can't use it for some reason, we can delete it for you. But please don't do it by manually destroying content.

Terrific talk, Steve. I enjoyed it very much.

@DavidRoberts To ask for what? He/she has the ability to unaccept and accept a different answer.

In view of Cole's answer, it might be worth reconsidering whether this should be the 'accepted' answer.

@FilippoAlbertoEdoardo It looks to me that Romagny is talking about something else, about single duals.

Regarding the second paragraph after the fold, it's definitely true that the free closed monoidal category on a category exists.

My friend Jim Dolan (of Baez-Dolan fame) has hundreds of notebooks.

Weird. The more usual conjecture is that it consists of just one point.

@YemonChoi By my reading, the students were not professionals, unless by "professional" one includes "intending to become a professional" (and how would one know that?). Actually, I am conflicted about calling Egan an "amateur" -- to me he walks and quacks just like a professional.