In this major book the acclaimed author of Language Truth and Logic tackles one of the central issues of philosophy—how can we be sure we know anything—by setting out all the sceptic's arguments and trying to counter then one by one. In considering all the main philosophical issues involved—how we know that something is a fact, that our senses and memory don't deceive us, that other people are conscious in the same way that we are—he throws a clear light on the nature of our fundamental beliefs and provides an outstanding example of the philosophical mind at work.