Episode 7.15: Mad, Bad or Sad: what’s the difference?

Someone who doesn’t share our choices of goods and values is likely to behave in ways that we find strange, possibly even unacceptable. Typical responses are to describe them as one or more of mad, bad or sad, but is there really a difference between the three? If someone behaves according to a set of rational principles that we do not understand because the choices choices upon which that rationality are based are different from ours, when are they not likely to appear any one or more of mad bad or sad?