Some psychologists believe that we can explain every decision or choice that an individual makes by referring to some earlier conditioning that the individual has undergone, so that, although the individual might feel free, his or her action is in fact entirely determined by what has happened in the past, and by genetically transmitted predispositions. We cannot know for certain that this isn’t actually the case.
Philosophy: The basics
I don't know the use of "actually" in the context above. Is it redundant? Is there any difference between "this isn’t actually the case" and "this isn’t the case"?
I tried to understand the bold sentence like this: We cannot know for certain whether this is actually the case or not. Is my understanding correct?