Is the world an illusion?

This is the latest Question of the Month in Philosophy Now (Issue 127, August/September 2018). I don't enter them all, but I confess I wrote this one in half an hour, though I spent a lot of time polishing it. Some readers will note that it comprises variations on ideas I've expressed before. The rules stipulate that it must be less than 400 words, so this is 399.


There are two aspects to this question: epistemological and ontological. Dreams are obviously illusional, where time and space are often distorted, yet we are completely accepting of these perceptual dislocations until we wake up and recall them. Dreams are also the only examples of solipsism we ever experience. But here’s the thing: how do you know that the so-called reality we all take for granted is not as illusory as a dream? Philosophers often claim that you don’t, in the same way that you don’t know if you’re a brain in a vat.

The standard answer to solipsism is that you can be the only one, because everyone you know and meet can only exist in your mind. So the answer to the difference between a dream and reality is the converse. If I meet someone in a dream, I’m the only one who is aware of it. On the other hand, if I meet someone in real life, we can both remember it. We both have a subjective conscious experience that is concordant with our respective memories. This doesn’t happen in a dream. By inference, everyone’s individual subjective experience is not only their particular reality but a reality that they share with others. We’ve all had shared experiences that we individually recall, correlate and mutually confirm.

The world, which I will call the Universe, exists on many levels, from the subatomic to the astronomical. Our normal perception of it only covers one level which is intermediate between these extremes. The different realities of scale are deduced through mathematics and empirical evidence, in the form of radio waves collected in an array of gigantic dishes (at the largest scale) to trails of high energy particles in the Large Hadron Collider (at the smallest scale). Kant once argued that we can never know ‘the thing-in-itself”, and he was right because the thing-in-itself changes according to the scale we observe it at.

In the last century we learned that everything we can see and touch is made of atoms that are mostly empty space. It requires advanced mathematics and a knowledge of quantum mechanics (using the Pauli Exclusion Principle) to demonstrate how it is that these atoms (of mostly empty space) don’t allow us to all fall through the floor that we are standing on. So we depend on the illusion that we are not predominantly empty space just to exist.


I wrote a much longer discussion on this issue (almost 2 years ago) in response to an academic paper that claims only conscious agents exist, and that nothing else (including spacetime) exists 'unperceived'.