Perhaps the core of the Wager is that it assumes a human being has the ability to believe something by an act of will: not just to say one believes it but to actually, sincerely, believe it to be true. This is known as doxastic voluntarism; it is probable that most people lack the ability to do this deliberately. Beliefs are often involuntary; at the very least you possess an involuntary belief that you experience the world. Further, you have an involuntary belief that someone, somewhere, at some point in time, typed these very words. Similarly, it is difficult to believe things you know to be untrue. Consider how you would respond if someone told you to believe that the earth rested upon the back of a giant turtle. Even if you were inclined to, it is doubtful whether you really could genuinely believe it. Pascal attempted to "solve" this problem by saying that a nonbeliever should associate with believers, attend religious services, etc. until this inspires belief in them—essentially "fake it 'til you make it." The effectiveness of this is highly questionable though.
Freedom of action, however, is significantly different. This is something that people have considerably more free will to exert — so someone is free to worship God without believing. The question, therefore, is whether God has the ability to detect such a ruse or such belief in belief, or whether God would be happy to have people "fake" their beliefs in such a way.
Pascal's Wager must, at the very least, make one of the following assumptions:
That doxastic voluntarism is possible.
That God doesn't care (or doesn't notice) if you "fake it".
One of those is known to be wrong, the other is theologically questionable.
