Philosopher Mark Kingwell thinks about thinking for yourself in an era of radical know-it-all-ism. "Question authority," the popular 1960s slogan commanded. "Think for yourself." But what started as a counter-cultural catchphrase, playful in logic but serious in intent, has become a practical paradox. Yesterday's social critics are the tone-policing tyrants of today, while those who claim "colourblindness" see no need to engage with...