What Does It All Mean? A Very Short Introduction To PhilosophyThomas Nagel

How do we know anything? Nothing at all exists except the inside of your mind; all your arguments would be rendered invalid because all your beliefs come through the evidence of your senses, from inside your mind The most radical conclusion would be that your mind is the only thing that exists. This is called solipsism. On the other hand, it is too much to claim that you are the only one that exists, since you can't know on the basis of what's inside of your mind that there's no world outside it This may be the right conclusion: You don't know anything beyond your impressions and experiences. There may or may not be an external world, which may or may not be completely different from how it seems to you there's no way for you to tell. This is called skepticism about the external world.