Really hard question. A lot of psychologists reject this question as being meaningful, because they say there is no sensible definition of what free will actually is. One way to look at this is to ask this question: when we sense that we decide to perform an action, is that sense of decision actually causing the action. There’s a very famous experiment by a psychologist called Benjamin Libet. He asked his participants to do a very simple thing – just wait for a moment of their own choosing, any time they liked, and then bend their finger. He measured the moment when they reported making the decision (they were looking at a clock and said the time on it when they made the decision), and also the moment the bent their finger. Unsurprisingly, people report deciding to bend fingers just before they bend their fingers. But (here comes the freaky part) he also measured brain activity in the motor cortex – that’s the part of the brain that plans and carries out actions. What he found was that there was a spike in brain activity BEFORE the participants decided to carry out the action. So in other words, before the brain parts that cause the sense of voluntary action were active, unconscious bits of the brain had already “decided” to cause the action. One of my favourite books is called “The illusion of conscious will”. In it, Daniel Wegner argues, based on experiments like this, that the sense we have of causing our own actions is an illusion. I think the arguments are strong, so I lean towards believing that free will isn’t what it’s cracked up to be.