Agreement in a copulative clause: "... es, en sí mism(o|a), una ..."

Question

I've noticed that Spanish is a bit tricky when it comes to agreement in copular clauses. The following sentence still caught me a little off-guard though:

El deseo de una experiencia más positiva es, en sí misma, una experiencia negativa.

I would have expected "misma" to agree with "el deseo". As written, I'm about 50/50 between thinking that this is just how Spanish works, and "misma" agrees with the trailing "una experiencia negativa", versus this being a mistaken agreement with the preceding "una experience positiva".

Answer 1

This is a mistake in the source text. It's understandable, like other failures of agreement when several sentence constituents are subordinated or linked to each other in a more-or-less complicated arrangement, but it's still a mistake. Just as you expected, it should be

El deseo de una experiencia más positiva es, en sí mismo, una experiencia negativa.

This is because the reflexive expression sí mismo can only refer to the previous noun phrase (the subject) as a whole (el deseo de una experiencia más positiva), which is headed by the masculine singular noun deseo; it cannot refer to the subordinate noun phrase una experiencia más positiva. The comment en sí mismo is an adverbial complement that modifies the verb, and because of how Spanish works, this means any pronouns inside it can only refer to the subject.