I believe in free will (even though I don’t believe in the supernatural), and I think I can even argue for a mechanism that allows it to exist.
To me, the free will problem seems similar to ideas that existed early in physics: Namely, if you could know–with absolute accuracy–the position, velocity, and direction of every material object in the Universe at a specific moment in time, then you could calculate the entire past and future of the Universe . . . rather like stating that you could predict how the dice will roll if you knew the air resistance, the position of your hand when throwing the dice, how hard you throw the dice, and so forth.
Well . . . this all turns out not to be true. Even if you did precisely know all physical parameters before you cast the dice, you will still be wrong much of the time.
This is because of a certian “graininess” to the Universe that is defined by the Uncertainty Principle.
This means that even if you knew the precise and exact location and velocity of every subatomic particle in the Universe, and you have a computer which is larger than the Universe and able to calculate as fast and accurately as you want . . . you would still not be able to perfectly predict a person’s behavior . . . while the person in question may be able to predict their own behavior just fine.
So, it’s either free will, or something that so closely resembles free will that we can’t distinguish it from free will . . . so we may just as well call it free will, pending future discoveries that should shed more light on the question.