Can we know what we don't know

How can we know whether we are living in a world of actually existing things - or a simulated pseudo-reality?

Our experience tells us about a world made up of material things. It makes us believe that these things exist independently of us. And she wants to make us believe that we can know this too. Nevertheless, philosophers have devised so-called “skeptical scenarios” over the centuries. The aim is to cast doubt on at least one of the above three assumptions. So there are at least three different ways we can be wrong about the world.

First, we might be wrong about the fact that the world is actually made up of material things. For example, Bishop George Berkeley argued that the world is made up of ideas in the consciousness of God. However, ideas are not material objects. Nevertheless, he believed that this purely mental world is independent of us, because we are part of an objective world created by God from ideas.

Second, there is the possibility that the non-material world we experience is entirely dependent on us. Although the world appears to be inhabited by a myriad of people, we are actually alone. The whole world would turn out to be a mere fabrication of our minds. This is the most radical, skeptical and so-called solipsistic scenario.

Finally, there is the Pyrrhonic skepticism. The world is indeed material and independent. But how can we know anything about this world? The real world is on the other side of an unbridgeable chasm. We remain trapped in the “bogus reality” of experience.

Bertrand Russell claims that we can get rid of the most radical of these scenarios, solipsism, with relative ease. When you get home after a long day at work, your cat (if you have one) will greet you more or less happily. She will appear alive to you, but will likely be quite hungry. Even though you fed her in the morning before you left the house. If the cat were a mere product of your imagination, it shouldn't change if you don't think about it. Then why did your cat get hungry while you sat in the office thinking about other things? The best explanation for this, Russell argues, is that whether you are thinking of her or not, your cat leads a life of its own.

According to the Pyrrhonic skepticism, the world may be material and exist independently of us. But we can doubt whether it is actually the way we experience it. In other words, the gap between our experiences and the world is too wide for us to bridge. It could turn out that everything is different from how we experience it and that we live in a mere “pseudo-reality”. There is a way we can respond to this difficulty. Even if we cannot know anything about the nature of things themselves, we can still know, on the basis of our experience alone, how these things, unknown to us, are spatially and temporally arranged. So we know how three celestial bodies have to be arranged in order to experience a solar eclipse. And we know this without knowing more precisely about the nature of these heavenly bodies.

That would have done with Solipism and Pyrrhonic Skepticism. Unfortunately, we could still live in the Matrix. For example, contemporary philosopher Hilary Putnam developed the famous skeptical scenario: How can you know from all of your experiences that you are not a brain in a tank, artificially kept alive by a team of evil scientists, and electrically like that stimulates that you believe that you are actually experiencing the world as you think you are experiencing the world? If you think this scenario is plausible, then you accept that there can be absolutely no correspondence between your experiences and your surroundings. In the scenario, your environment consists of nothing but a tank, some nutrient fluid, quite a few wires, and other electrical equipment. But you are now experiencing that you are reading this article. Many philosophers do not accept this conclusion. Putnam also argued that our experiences depend on the nature of our surroundings and the corresponding causal relationships. And if that's true, then all you would experience in the tank is the tank, the nutrient fluid, the wires, and the electrical equipment. But you don't, which is why it is implausible that we could live in the matrix.

Unfortunately, this answer is rather unsatisfactory as it cannot completely exclude the matrix scenario. The only thing we can say is that it is implausible (but not impossible) that we live in a world where there are no trees, no animals and no tomatoes, although we constantly have experiences of trees, animals and tomatoes .