On one hand, since I believe in the scientific approach, I don’t accept free will. Instead, I believe that human behavior is determined by the laws of nature, and where those laws are non-deterministic, our behavior is truly random.
However, I find I must assume free will or my world will be overturned. For example, without free will, ethics loses its significance. Of course, people will still behave ethically most of the time because of law enforcement, selfish genes and upbringing, but in the phrase “thou shalt not steal” the word shalt becomes meaningless.
Political freedom, too, becomes pointless. In the absence of free will freedom turns into recognized necessity. What difference does it make then if the state makes its citizens recognize a different necessity?
But science itself, paradoxically, needs free will, too. In experiments, independent variables are used to test causality. But how can a variable be independent in the absence of free will?
All of this is not to say that free will exists; rather, it’s a simplified model we have to contend ourselves with until we have a better one, in the same way that physics freshmen are implicitly taught that Consciousness causes collapse because we don’t yet have an established “correct” interpretation of quantum physics.