Stephen Asma tries to get a handle on it:

[T]he soul is meaningful to many of us without any scientific verification of its existence.

That is not the same as just having faith in the soul despite a lack of evidence. I'm not suggesting that familiar view. What I'm suggesting is more slythe soul can be deeply meaningful whether it exists or not, and it can be deeply meaningful even if you disbelieve in its literal, metaphysical existence. That is not the usefulness of fictions and delusions. It's the usefulness of an expressive folk language that can't be replaced by a scientific language.