Free will exists if there is a possibility of change, if there is movement, and as is evident to the senses, movement exists, therefore there is change, therefore there is free will.

If everything was determined, everything would be static, and everything would cease to move.

Liberty has to do with how capable we are to enjoy our free will, not with whether we have it or not. We are free to the extent that there are no options disabled by our own inner fear/lack of control.