“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 it’s important that there is a reason for clients who reject free will.
Suppose we have no free will. Two claims are 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 positive!) and behaviour.
So, therapy may just be another link in the big causal network in the universe. Hopefully it’s more likely to improve someone’s life than other links, however unavoidable and predetermined going to see the therapist and its consequences might be.