I think Socrates was wrong. He said "I think, therefore I am" (in Greek of course), but I don't think that is really true. I think it should instead be "I think therefore I was." as when do you really stop existing? You might have thought that, but before you can reflect on that thought, you already died or vanished. As such any reflection on that thought can only happen in the future, which you can't perfectly predict. Case in point, Socrates isn't anymore, but he did think, which did prove that he was, but not that he is.

But maybe Socrates just wanted to provoke people to bikeshed instead of making a careful statement!