Do our sense experiences tell us about the “real” world?

As a teenager, I spent a lot of time thinking about the meaning of life, as many do, and what we can really be certain of. At that time I wrote some plays in the style of “radio plays” and some of my friends acted them out to be circulated on tape.

One of those plays was called “A voyage to infinity”.

This was long before films like “The Matrix” and long before phrases such as “virtual reality” and “artificial intelligence” had even been coined. I had not heard of Descartes and his “evil demon” but the possibility that the information we received through our senses did not portray the real world but came from some other source had occurred to me.

In the play, some travellers manage to discover that all of us were simulations in large computers, Matrix style, and what we thought was the real external world was an illusion. The actual real world which they found was very different to what they had perceived.

I found this possibility deeply unsettling. The ground we stand on is far less certain than we think.

If we did live in a virtual world, such as is depicted in the film “The Matrix”, then no experiment which we could ever do would reveal this.

We rely on our senses for everything we know but we cannot tell where these sights and sounds are coming from nor know if they are giving us a true picture of the external world.

This might seem self-evident but there are philosophers who point out that our senses evolved in order to enable us to survive and not to tell us the truth eg.[Hoffman 2020]. Not only do our senses provide an approximation to reality but what we see is more like the user interface on a computer. While such a UI can enable us to manipulate files and documents, the icons on the screen do not resemble, in any way, the hardware behind them.

In this model, science is a way of finding out how the UI works and how to use it to get the results we want but we cannot get knowledge about what is under the bonnet.

This kind of idea has been tested by a number of well known thought experiments.

Rene Descartes famously attempted to find out what it was possible to be certain of. He started with the knowledge that he existed, based on the fact that if he was thinking then there must be a thinker.

To illustrate how little we can know, he imagined  the possibility of an “evil demon” who had taken a brain and connected all the inputs and outputs to some sort of data source. Others have spoken of a “brain in a vat” to mean the same thing and the film “The Matrix” gives a dramatised version. There is no way that we could tell whether we were in this unfortunate condition or whether we really were seeing things as they are.

Descartes didn’t get much further without getting embroiled in circular arguments.

Others have tried to prove that the world we perceive is the “real” world, such as Bertrand Russell, Hilary Putnam, Henry Moore and others. I find none of their arguments convincing and would not want to put any faith in them.

David Chalmers [Chalmers 2009] takes the view, which I share, that we cannot know whether we are in a simulation or not or whether we see the real world or a User Interface to it, but that this makes no practical difference to us.

Whether the underlying reality is based on atoms, a multi-dimensional Hilbert space, vibrating strings or computational processes makes no difference. The scientific endeavour can continue regardless and our investigations of the world yield information about the environment that we are in whether that environment is “actual” or “virtual”.

Without suggesting that we really are actually living in a virtual Universe, what this shows is that it is not hard to imagine that there can be aspects of reality to which we simply are unable to access or even be aware of. Not only can we not know whether our Universe is “actual” or has been constructed by some agent using an actual Universe as the substrate, we cannot find out anything about the origin of our Universe at all, neither how nor why it came to exist or the whether an agent created it.