But as long as someone can change his mind, it’s false.
The influences that ultimately cause one to change one’s mind are largely mysterious for any particular decision, as the degree of influence is indeterminable or immeasurable and humans have a tendency to backwards rationalize their decisions or behaviour.
These mysterious influences include environmental factors, your genetics, your conditioning, etc. All of which, are out of your control — you are not
always in control of your environmental factors, you did not choose your parents & therefore your genetics, and your reaction to your conditioning is largely based on your genetics (and vice versa is also true).
Don’t confuse free will with voluntary action.
Sam Harris’s argument against free will isn’t that we lack voluntary action or that there is no point in doing anything if we lack free will, it’s more so that the invisible forces that influence what we ultimately do or don’t do & shape our personalities are outside of our freedom to choose and therefore we are not free agents, but rather products of cause & effect.
Sam also points out how thoughts just spontaneously appear and that we can’t think thoughts before we think them, and therefore we cannot be the authors of those spontaneous thoughts, making the case we don’t necessarily have the freedom to choose our thoughts and thus our behaviours/actions.
Now although I find Sam’s overall argument against free will compelling and true, I do not live my life as if free does not exist. I don’t think it’s practical to do so anyway.