The importance of understanding the nature of scientific knowledge -- The traditional account of knowledge -- Belief -- Truth -- Justification -- Evidence -- Basing a belief on the evidence -- A problem for the traditional account of knowledge -- Explanation and understanding -- From explanation to knowledge -- Skepticism about the external world -- Skepticism about induction -- Empirical evidence of irrationality -- Anti-realism about science -- Gaining scientific knowledge from others -- Knowledge in a scientific community -- Looking back and looking forward.