Many great minds, through the centuries, have tried, without success, to solve the free will versus determinism controversy. I believe this controversy has persisted because it is a false dichotomy stemming from the assumption that free will must be independent of, or opposed to, causality. As I'll try to explain, free will is produced when human intelligence interacts with the world around us (causality). There is no conflict between free will and causality/determinism. No dualism. It's entirely natural.
First, let's get our terms out of the way.
Here's some brief descriptions of concepts I'll be using. The names of these concepts will be bolded.
Free will is a controversial concept. People can't agree on what it means. Most folks think of free will as volition: the ability to make a choice and act upon it. As I'll explain below, that's not quite right.
The law of causality (cause and effect) states that: "every material effect must have an adequate antecedent cause". There are no uncaused effects. Science relies on this fundamental law of nature. Everything, everywhere (outside the quantum realm), is subject to causality. Including humans.
Causal factors are the conditions and elements that contribute to an event or effect.
As you probably know, determinism is all about causality. Determinism implies that, if you could know all the causal factors of a closed system, you could predict it's state for any future point in time.
Consciousness is an interplay between our brains, our sensory organs and the world around us. If we never had any one of these components, consciousness could not exist; there would be nothing to be conscious of.
Time is the 4th dimension. It's linear: it has just one direction and is continually unfolding into the future. This post will not concern itself with esoteric scenarios of time; we are concerned only with the human, temporal, experience of time.
Now that I've got the description of terms out of the way, I'll lay out my explanation of free will as best I can.
Our brains have evolved to anticipate the future. It's hardwired into us. We wouldn't be able to function without this ability. For instance, if I suddenly said, "Hey you, catch this!", and threw a ball at you, you would extend your hand out to where the ball will be when it arrives - not where the ball was when you first saw it. Our ability to anticipate the future (causality) has a lower limit (reaction time), of about half a second. If it took less than half a second for the ball to arrive, you probably could not have caught it.
We can anticipate the future a half second from now or a half century from now or anything in between. When we anticipate beyond the immediate future, we use words like "strategy" or "plan" to describe anticipation. We are so inured to anticipation (short-term or long-term) that we take it for granted. But we, in fact, anticipate constantly.
Anticipation is not an ephemeral wisp that flits through the mind and is gone. We mentally revisit our plans to revise or adjust them as needed. This is one of many forms of feedback our brains routinely perform. Mental feedback, like anticipation, is another feature of the mind that we take for granted and could not function without.
A Temporal Advantage:
Our ability to anticipate the future and adjust our plans accordingly represents a temporal advantage over causality. Causality must wait for the future to arrive in the present but we can anticipate causality and be ready for it when it arrives. Of course, our plans don't always work out but they usually do because we adjust our plans when we think it necessary.
Causality does not conform to our plans. Our plans (with any luck) conform to causality. Causality does not stop at the human skull - our brains are also ruled by causality. But this doesn't mean we're automatons controlled by external forces. We have anticipation and mental feedback to thank for that.
We are goal-oriented creatures. When we anticipate the future, then make or adjust our plans accordingly, that is mental feedback at work. It is through mental feedback that we direct our actions, step by step, toward our goals. Remember: causality does not stop at the human skull. It's not just the world around us that supplies causal factors - our own brains, via mental feedback, also contribute causal factors.
Self-Determinism is Free Will:
We are constantly flooded by causal factors from the world around us and from less tangible causal factors like experience, heredity, education, emotions, culture and ethics, to name a few. One of the most significant causal factors to get thrown into this mix is our own mental feedback. Because this feedback stems from our own consciousness (self), it carries a lot of weight as a causal factor. Causality determines our actions but thanks to mental feedback those actions are largely self-determined. It's a paradox. We have no choice but to exercise free will. When causality meets human intelligence, determinism becomes self-determinism. And self-determinism is free will.
Everything is determined by causality. Mental feedback is a causal factor but that doesn't mean that it will necessarily prevail. Other causal factors (heredity, ethics, an unexpected development, etc.) could override our mental feedback. For instance, you might plan a crime or other dasterdly deed but find that you're unable - because of your ethics - to perform the deed when the time comes to follow through.
To the extent that we can anticipate causality and follow through with our plans, we are self-determined. This, to me, is what free will is: the ability to act in self-determined ways. If free will is, essentially, self-determinism, then the notion that we are in control of our own destinies is not quite true. It's not a matter of control: it's a matter of adjustments. And even then, other causal factors can completely derail our plans and alter our destinies. We are not above or outside the control of causality: we are integrated with it. Anticipation gives us a temporal advantage over causality that enables mental feedback to adjust our actions if necessary. To the extent we are successful at anticipating causality, we are masters over it and are marching into the future in self-determined ways.
Free will is an emergent property of human intelligence; it's a product of causality - not independent of it - and, thus, is not absolute. But we normally do what we want and live almost entirely in self-determined ways. That is what free will is all about.