Many ancient and modern thinkers have made this claim. They have usually been strong determinists, from Hobbes to Einstein.

Classical compatibilists, from Hobbes and Hume on, have held that free will exists but that it is compatible with determinism (actually many determinisms).

Since the discovery of irreducible quantum mechanical indeterminism, most scientists and some philosophers have come to understand that determinism is a dogmatic belief unsustainable from the evidence.

It is determinism that is the illusion.

Nevertheless, most philosophers remain compatibilists, even as the evidence of indeterminism has caused them to declare themselves agnostic on the truth of determinism or indeterminism.

Some illusionists claim it will do society good to recognize the illusion of free will. Many simply want to eliminate all retributive punishment of criminals. Others, following Peter Strawson and David Hume's naturalism, want to hold on to the ideas of blame and praise. They defend a compatibilism between determinism (or indeterminism) and moral responsibility.

Thus a few compatibilist/determinist philosophers have, following Strawson, turned the conversation away from the "unintelligible" free will problem to the problem of moral responsibility. They include John Martin Fischer and a number of his followers, who call their position semicompatibilism.

They basically abandon free will as incompatible with determinism (or indeterminism) and hold onto moral responsibility as compatible, but their positions are all subtly nuanced, depending on their stance with respect to the existence of alternative possibilities.

Some tougher-minded illusionist philosophers call themselves "hard incompatibilists," including Derk Pereboom, Galen Strawson, and Saul Smilansky.

They deny the existence of both free will and moral responsibility.

Pereboom, Smilansky, Galen Strawson, and the psychologist Daniel Wegner explicitly say that free will is merely an illusion. They differ on whether the illusion is a problem or a benefit for society.

Illusionism is the position that illusion often has a large and positive role to play in the issue of free will. In arguing for the importance of illusion, I claim that we can see why it is useful, that it is a reality, and why by and large it ought to continue to be so. Illusory beliefs are in place concerning free will and moral responsibility, and the role they play is largely positive. Humanity is fortunately deceived on the free will issue, and this seems to be a condition of civilized morality and personal value.

In his 2002 book, The Illusion of Conscious Will, he says

So, here you are reading a book on conscious will. How could this have happened? One way to explain it would be to examine the causes of your behavior. A team of scientific psychologists could study your reported thoughts, emotions, and motives, your genetics and your history of learning, experience, and development, your social situation and culture, your memories and reaction times, your physiology and neuroanatomy, and lots of other things as well. If they somehow had access to all the information they could ever want, the assumption of psychology is that they could uncover the mechanisms that give rise to all your behavior and so could certainly explain why you picked up this book at this moment. However, another way to explain the fact of your reading this book is just to say that you decided to pick up the book and begin reading. You consciously willed what you are doing.

These two explanations are both appealing but in different ways. The scientific explanation accounts for behavior as a mechanism and appeals to that part of us that knows how useful science is for understanding the world. It would be wonderful if we could understand people in just the same way. The conscious will explanation, on the other hand, has a much deeper grip on our intuition. We each have a profound sense that we consciously will much of what we do, and we experience ourselves willing our actions many times a day. As William James put it, "The whole sting and excitement of our voluntary life ... depends on our sense that in it things are really being decided from one moment to another, and that it is not the dull rattling off of a chain that was forged innumerable ages ago" (Principles of Psychology, 1890, 453). Quite apart from any resentment we might feel on being cast into the role of mechanisms or robots, we appreciate the notion of conscious will because we experience it so very acutely. We do things, and when we do them, we experience the action in such a way that it seems to flow seamlessly from our consciousness. We feel that we cause ourselves to behave.

The idea of conscious will and the idea of psychological mechanisms have an oil and water relationship, having never been properly reconciled. One way to put them together — the way this book explores — is to say that the mechanistic approach is the explanation preferred for scientific purposes but that the person's experience of conscious will is utterly convincing and important to the person and so must be understood scientifically as well. The mechanisms underlying the experience of will are themselves a fundamental topic of scientific study. We should be able to examine and understand what creates the experience of will and what makes it go away. This means, though, that conscious will is an illusion.

It is an illusion in the sense that the experience of consciously willing an action is not a direct indication that the conscious thought has caused the action.

And in the end it is quantum mechanics that provides the ultimate breaks in the causal chain of all determinisms needed to ensure human freedom and creativity.

The trick is to show that the random chance of quantum uncertainty does not also put actions out of the agent's control, as claimed in the standard argument against free will.