“If behavior were unavoidably determined, there would be no reason to practice psychoanalytic therapy or, for that matter, any form of therapy.”
Although I’m not sure about free will, I don’t think this is a necessary consequence of having no free will. And maybe that there might be a reason is important for therapists with clients who reject free will.
Suppose we have no free will. Two claims still seem difficult to refute:
(1) We experience stuff, some of it fun, some of it not. The phenomenological feeling which goes along for the ride doesn’t seem to care about free will. Related to this, I think it’s interesting that we still go to the cinema and read books even though we know the ending has already been decided: we seem to derive great pleasure from finding out what happens next.
(2) Chatting to people partially determines our future experience (sometimes fun!) and behaviour.
So therapy is just another link in the big causal network in the universe. Hopefully it’s more likely to improve someone’s experience than some other links, however unavoidable and pre-determined going to see the therapist might be.