An illusion is “1. An instance of a wrong or misinterpreted perception of a sensory experience; 2. A deceptive appearance or impression; or, 3. A false idea or belief.”
Of course, we’re familiar with illusions. From optical illusions like blood flowing from a glacier in East Antarctica to sleight of hand illusions like Mack King’s amazing Rope Trick, we run into them all the time. In general, we are good at spotting them. We know that Mack King is just performing a trick. We know that blood isn’t flowing from a glacier—its runoff from iron deposits under the glacier. Fine. But, have you ever been truly deceived by an illusion. I have. I’m sure you have too. And, in any case, I’m sure we agree it’s possible to be tricked by one.
This is where illusions become interesting. What if you were being tricked by illusions every day and didn’t know it. This is exactly what some scientists and philosophers believe. They suggest that some of our most basic beliefs, our clearest intuitions about the nature of reality, are just illusions—things like consciousness and free will, morality, and design in nature. Consider some examples:
“Free will is an illusion. Our wills are simply not of our own making. Thoughts and intentions emerge from background causes of which we are unaware and over which we exert no conscious control. We do not have the freedom we think we have.” —Sam Harris “Like the ingenious user-illusion of click-and-drag icons, little tan folders into which files may be dropped, and the rest of the ever more familiar items on your computer’s desktop. What is going on behind the desktop is mind-numbingly complicated, but users don’t need to know about it, so intelligent interface designers have simplified the affordances, making them particularly salient for human eyes, and adding sound effects to help direct attention. Nothing compact and salient inside the computer corresponds to that little tan file-folder on the desktop screen…Curiously, then, our first-person point of view of our own minds is not so different from our second-person point of view of others’ minds: we don’t see, or hear, or feel, the complicated neural machinery churning away in our brains but have to settle for an interpreted, digested version, a user-illusion that is so familiar to us that we take it not just for reality but also for the most indubitable and intimately known reality of all.” —Daniel Dennett “The position of the modern evolutionist...is that humans have an awareness of morality...because such an awareness is of biological worth. Morality is a biological adaptation no less than are hands and feet and teeth.... Considered as a rationally justifiable set of claims about an objective something, ethics is illusory. I appreciate that when somebody says “Love thy neighbor as thyself,” they think they are referring above and beyond themselves.... Nevertheless...such reference is truly without foundation. Morality is just an aid to survival and reproduction...and any deeper meaning is illusory…” —Michael Ruse
“The beauty of biology, really, is the illusion of design,” —Richard Dawkins
What each of these men purports to do is to take us behind the scenes of life and explain why we are mistaken in some basic belief. They want to help us take the virtual reality headset off and see life for what it is. I must tell you, this makes me wonder, what do they know that we don’t? I mean it’s one thing if they point to a magician and say, “That’s a trick!” But, it’s another thing altogether when they point to our most basic beliefs, our strongest intuitions about reality—I am freely choosing to write this blog right now, for example—and say, “That’s an illusion!”
So, here’s the answer. the authors mentioned above begin with the same belief—that all that exists, in reality, is the physical (Physicalism). We are only matter and nothing else. From this belief, all their conclusions about “illusions” follow necessarily. Why don’t we have consciousness and free will? Because there is no soul. You don’t have a mind. You have a brain that receives inputs from its environment via nerves and then reacts by sending signals via nerves to your body. There is no “you” in there actually making decisions. There can’t be. “You” are just matter. Why aren’t morals real objective truths? Because we are just matter. Matter has no moral qualities. It has size, shape, motion, location, etc. But, it is not good or bad and cannot be right or wrong. And, why isn’t there any design in nature? Why shouldn’t I think that the countless creatures on earth are amazing machines designed by the most brilliant engineer ever? Because, if only matter exists, then God can’t exist.
In other words, these things must be considered illusions and explained away. Physicalism requires it. Otherwise, they start to seem like really good evidence for the existence of a spiritual realm. The more I think about it, the more I think these things seem like evidence that Physicalism is the real illusion.
 Here’s a nice basic explanation of the rope trick: https://www.youtube.com/watch?v=Rgg_LhbfWxI
 Harris, Sam. Free will. New York, Free Press, 2012, p. 5.
 Michael Ruse, “Evolutionary Theory and Christian Ethics,” in The Darwinian Paradigm (London: Routledge, 1989), pp. 262, 268-9.