Not Everything Can Be An Illusion

One of the great functions of epistemology is to separate what merely appears to be true from what is true, what seems to be from what is.  There is a word for something that merely appears a certain way but is actually different: illusion.  An illusion is something that seems to be real but is not.  Sometime in the past, perhaps, you have heard someone suggest or propose that "everything is an illusion," and perhaps this suggestion caused a great deal of anxiety.  No one needs to suffer fear over an impossible thing.

It is impossible for everything to be an illusion, for if everything is an illusion then there is no distinction between illusion and reality and thus the illusion is reality, meaning that there wouldn't be such a thing as an illusion to begin with.  Thus, some things can be illusory--some things can have misleading appearances, but not everything can, or else illusion would not and could not exist.  Truth is the way things are, and if there was no such thing as truth, it would be true that truth does not exist.  There cannot not be a way that reality is.

What are some individual examples of more specific things that cannot be illusions?  To perceive an illusion requires consciousness, and thus consciousness itself cannot be an illusion; my consciousness, at least, is inescapably real (I am not a telepath and so I am not aware of whether or not other minds exist).  Logic cannot be an illusion, because a thing cannot be anything other than what it is, and a thing being what it is excludes it from being what it is not.  Axioms, the existence of truth being one, cannot be illusions; they are necessary truths that are true regardless of what else is.  There is no way that they can be false because they apply by necessity to all things, to all possible worlds.

There is one way to sort illusion from reality, up to a point depending on the issue at hand--rationalism alone can liberate people from uncertainty while generating new uncertainties.  With necessary truths established, logic reveals other things that cannot be illusions.  For instance, although my perceptions of the external world might be drastically different than the actual nature of the external world (I could be a brain in a vat or deceived by a demon into misperceiving external objects), the existence of matter is absolutely certain, since I experience physical sensations and cannot do so unless physical matter of some kind exists.  The existence of matter, whatever its actual appearance, cannot be an illusion, just as logic and my consciousness cannot be.

A great many things that seem a certain way might still turn out to be quite different than my perceptions would suggest.  But not everything can be an illusion, and some things in particular cannot be by their very nature.  May those who doubt find some existential peace in knowledge of what cannot be false!  I know how terrifying an existential crisis can be.  Yet there are some things which we need not be burdened by, for rationalism sets us free to know some truths and to pursue the rest.