Apparently, the best way to avoid illusions is just to "stick to the truth", which, incidentally, is what most people say they do. Both skeptics and religious fanatics claim to have found a truth, the truth, and yet... they disagree... how can we be sure which one is right, or if there is anyone who is right in ascertain that he has found the truth?
I must confess that I am terribly romantic and that my main constant passion in life has been for the truth. I have pursued it in religions, science, philosophy, mysticism, etc. I must say I have never found convincing reasons to take anything as an established truth.
Religion relies too much on inner feelings and intuitions of which we do not understand the origin or validity, no matter how comforting and enlightening they may be.
Science is always overcoming itself, restructuring the very foundations just to achieve small differences in its predictions (at least initially, like in the Copernican revolution, and then in Einsteins theory of gravity). So how can we trust our present theories? In the billions of years in which a scientific civilization may evolve will not many other paradigms be found, that will completely reshape our vision of things? I find it highly improbable that even a mere million years of evolution will not bring an almost completely different vision of our universe.
Mysticism was a mystery when I started to venture in its core, but I came to believe that its essence has nothing to do with truth or falsity, even less like something that can be put into a theory. In my view Mysticism's value to the world is in making people free, it is in the discovery and cultivation of freedom of each one's core freedom that its value resides. Mysticism taken as a (set of) theory(ies) is as unwarranted and dangerous as religion.
Philosophers disagree in almost everything, so both skeptics and constructive thinkers, taken together with the fact that no one has presented a valid argument to demonstrate even the most basic truths (like the falsity of solipsism, or that the world we see is not a simulation, that mathematical truths are real, that the sun will rise tomorrow, etc) is itself the best proof that the truth, if it was ever found, could not be proven.
Mathematics and other abstract sciences have an equivocal relation with reality and, although they appear obvious at first, they loose all that evidence after generations have advanced in their comprehension. For instance, at first it seems more than obvious that two straight parallel lines could never touch. Well, it seems they can, in geometries with more than three dimensions, and, more to the point, we seem to live in such a world. When irrational and imaginary numbers were presented for the first time they were badly received, like an anomaly, something that would go away after a while. And, yet, the opposite seems to have happened, they seem pervading and unavoidable in our mathematical fine-grained depiction of nature. Besides no mathematician can demonstrate that the world is more than a dream or a simulation. Perhaps all the mathematical and logical truths we see are nothing more than illusions, falsities, imprinted by those who control the dream or simulation.
So, as you see, although I am a true lover for truth, still in love, passionate love even, I can't say I possess it. I search for it, I desire it, I want to have it. But I must recognize that I was never able to grasp it fully, to possess it, to know it inside out. Instead, like a lover who likes to keep the light of passion alive, she keeps showing me little bits, here and there, that may or may not be, her true self. Keeps me wanting to know more and more about her. And, in the end, I am where I started in terms of possession, although I've slowly gathered, in all these games, a lot of imaginary images of how her true self might partially be. Perhaps in part she is like a machine, like a robot, using feelings as fuel, or perhaps in part she is love at the core, using images of machines to keep the game of love going, or perhaps it is something not so interesting from a human perspective, like a universal law, and the universe is as indifferent to our adventures as we are to the oceans of Jupiter.
In sum: we don't know, we live in a sea of mysteries.
So, how do we live in a sea of mysteries?
Well, first of all, truth is not necessary for action. It is only necessary to assure us that the action will meet the goal. For instance, David Hume as remarked that all our scientific or empirical knowledge is based on past observations, and, it seems, on the assumption that the future will be like the past. But how do we know that the future will indeed be like the past if we have not observed it yet? Hume said we couldn't, that even the most basic stuff, like, "the sun is going to rise tomorrow", was unproven without the unproven assumption that the future will be like the past. And that would happen with all scientific laws as well, because the fundamental forces that we ascribe to nature to explain what we see are themselves invisible. We ascribe them to nature to explain past events, but we cannot be sure that we have found the true fundamental forces that drive reality at its core because we have only seen part of reality (the past) and the end result of those fundamental forces (for instance two particles being attracted but not gravity or the electromagnetic or nuclear force itself).
So, we can act without being absolutely sure, betting that the sun will rise tomorrow, that we will not wake up in some completely different reality. But we can't prove nothing of that. We believe it for reasons that are open to debate. Hume said that it is the force of habit that makes us think that the future will be like the past. Inductivists in the XXth century have argued that it is more probable that something that has happened very often (like the fundamental forces continuing to have the same effects on the world) continues to occur. (It's like saying that a mysterious dice that has always showed the number 6, lets say for billions and billions of times, is extremely likely to continue to show the number 6 the next time it is rolled). Others like Karl Popper and Quine, have defended that, although no more than conjectures or atomically unproven, scientific theories are the best theories we have about the world, because they explain more, although they might be false.
What the lack of truth brings is a constant reminder, not only of our fundamental ignorance of what "the whole is all about", but, more interesting, of the need for us to get involved, to bet, to say: I will conjecture that science is that approach to reality, or that religion or mysticism is the best approach, or that being happy should in fact be our main goal, or be drunk and getting laid most of the time, preferably with lots of money to spend!
We can choose, being ignorant allows us, in fact condemns us, to choose is all freedom. Because no one can tell us, with absolute certainty, this is the way the world is. So goodbye to all leaders and sellers of the truth (me included). No one knows, and if someone did, he could not show it to us. Everyone has to make a bet.
Is this living an illusion? Is knowing that we do not know, that we live in a sea of mysteries, an illusion?
For me it isn't. Because I did not find, anywhere, a fundamental truth of which I could not doubt. Neither Biblical stories or even the Cartesian "cogito ergo sum". Biblical stories, and all the priests, just made me fearful of doubting. They say something like: «doubt is the way to hell. There is only one way out of doubt and that is believing. Believe and you'll be saved.» Well, saved from what? From doubt? Certainly. But is being saved from doubt a good thing? Only if certainty is better. And is certainty better? Well certainty obliges us to view the world only in a certain perspective. Someone who is free may see the world like the Evangelical Christian, the Mormon Christian, the Catholic Christian, the Protestant Christian, the Jew, the Buddhist, the Taoist, the Hindu, the Muslim, the Atheist, the Agnostic, the Sufi, the Aztec, the Materialist, the Communist, the Skeptic, and so on... But if you belong to some view, then you have made the bet that it is wrong for you to doubt that your particular view is the truth, or the best truth man can find. You are grinded by your view. Which is all very well, if it is in fact the truth. I don't see anything wrong in someone betting that, you know, Jesus, Buddha, Muhammad or Jah is the truth. I don't think this bet is an illusion, as long it is considered a bet by the person who does it.
Of course there is a temptation to say: «if the whole world is a big unknown, then what is the use of speaking about illusions? The truth is that we simply don't know, so all knowledge is illusive.»
This, in my view, is a dangerous fallacy. What is illusory is to take any knowledge as absolutely certain, as indubitable (this was famously shown by Descartes who doubted his own existence as a person and then went on to defend - perhaps ironically, given the religious fanaticism of the time - that God's existence was certain even though we could doubt the reality of the world and even the most obvious mathematical truths). For instance, perhaps the world is just a simulation, perhaps I was created a moment ago, with all my memories created with me. This is possible, but it does not change the fact that I need a key to turn my car on, that I have trillions of foreign bacteria living in our bodies, and that, as we speak, Saturn's rings have plenty of ice reflecting the sunshine. In other words, whatever the world is, it seems to function in a certain way. The fact that I have written this awfully long text shows it. It is possible to know this functioning although we can be sure that it will always work or what the world, as a whole, is about.
In other words, and borrowing from Karl Popper, we can say that all we have are conjectures, but that these conjectures work rather well and that they are not illusory when they are taken as nothing more than what they are: conjectures that work reasonably well for our practical purposes. They are like bets that usually give the expected result.
In fact this all mystery thing turns life into something quite agreeable. You have to put something of yourself, to make a bet, and then life responds to you. It is like a reply to a proposition. Perhaps if I sacrifice someone the volcano will calm. Will that work? Perhaps if I pray the disease will go away, or perhaps if I am able to throw all my fears and expectations away I'll be able to see how the planet and the human body works.
It's all a matter of choice and, like Popper also said, all we have are hypothesis which encompass conceptual theories but also behaviors, for any physical behavior can be interpreted as an unconscious conjecture (subjective knowledge) being tested against experience (for instance we are able stand up by having what can be interpreted as a very big number of expectations or hypothesis regarding the way the body is affected by gravity, all these hypothesis are constantly being reformulated - for instance, if we learn how to dance, ride a bike, jump on the trampoline, etc). The only difference is that, in this confrontation between conjecture and reality, man as learned to let theories die instead of himself.
Although some of us embrace the opposite view and are glad to bet with their lives on the truth of their conjecture. Notice, for instance, that many analytical philosophers today maintain that knowledge must be "a true, justified belief". In our Popperian view, nothing would qualify, for even Descartes famous dictum "cogito ergo sum" gains its strength by direct acquaintance, and could not be justified, for instance, if we suppose that we are nothing but a simulation.