What can we know?
“True wisdom is the knowledge that we know nothing”
Socrates
So what does all this investigation tell us about the underlying nature of the cosmos we find ourselves in?
Actually, very little.
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.
Before we can even get started with science, we need to accept at least two, unprovable, presuppositions:
Firstly we assume that our senses tell us the truth. 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.
Some workers have suggested that we are living in a simulated virtual world with the real world as an unknowable substrate, on the lines of the film “The Matrix”. Others eg.[Hoffman 2020] suggest that what we experience is akin to the user interface of a computer, not the computer itself.
However, as David Chalmers [Chalmers 2009] explains, although we cannot know whether we are in a simulation or not or whether we see the real world or a User Interface to it, this makes no practical difference to us. We can investigate our environment as much as we want and make predictions about the outcome of experiments regardless.
Secondly we assume that the laws of Nature that scientists discover operate not only at the time and place where the scientists perform the experiments, but everywhere and at all times. In other words that the Laws of Nature are universal. This is by no means self-evident and it is something which cannot be proved by science.
We believe with confidence that the sun will rise tomorrow because it has done so, as far as we know, for millions of years. However, as Bertrand Russell’s story of the Inductivist Turkey shows, this is not a guarantee. In fact all it would take is a single wayward asteroid to change it.
Although there are some people who maintain that the scientific method is objective and does not rely on faith, science is built upon these unprovable foundations.
Some would reply that these presuppositions are proved true by the success and predictive power of science. However it is very possible to get the right answer for the wrong reasons. For instance, Tycho Brahe’s model of the Solar System was successful in predicting the motion of planets but the model was later shown not to be valid more generally.
Other limits to our ability to know include our mental capacity to understand. Our brains are optimised to find patterns in the environment we inhabit and at the scale we exist in.
Even moving to another human culture can strain our understanding. Zooming out and looking at the Cosmic scale brings conceptual challenges which it is hard or impossible to visualise, such as “curved space” and time running at different speeds depending on the speed the observer is travelling and strength of gravity where they are.
Zooming in to the sub-atomic scale brings conceptual problems that even the brightest of physicists admit that they do not understand, such as quantum entanglement and quantum uncertainty.
Even though quantum mechanics shows us that we don’t know what the world is made of at the smallest levels, the truth is that we don’t know what the world is made of at all. Physics can tell us what material does but it does not tell us what material is. That is a completely different question.
We can find out about the externals of material but remain completely ignorant of the interior. That is something which is not aqccessible to us.