Errors and mistakes are of course common enough, and as often as not have unfortunate consequences. When we fail to do something we set out to do, we sometimes feel compelled to point to the errors and mistakes we have made, or sometimes less generously to the errors and mistakes others have made. For to be able to point to an error or mistake in this way is commonly thought to provide an explanation for what went wrong, and sometimes even to offer an excuse for it. In this paper I want to explore the significance of the terms ‘error’ and ‘mistake’ when we use them to talk about our failures. There are some good reasons for being interested in these matters. For some philosophers in the past have made much philosophical mileage out of our errors and mistakes, so much so that a whole breed of thinkers, sceptics, has come into being as a result. And I shall want to examine their attitude towards errors and mistakes, for it may turn out that the serious conclusions of the philosophical sceptic cannot rest upon the existence of either errors or mistakes, and as a result, are not so compelling as they might seem at first sight. In fact, I shall argue that our common experiences of error and mistake cannot support the weight that the sceptic places upon them. I also briefly look at the connection between error and mistake as I interpret them, and philosophical determinism. I argue that the existence of errors and mistakes is incompatible with conventional determinist philosophy.