Three and a half decades after avoiding punishment for bombing the Pentagon, Bill Ayers is still "guilty as sin, free as a bird," to use his own phraseology of 35 years ago. "For every human being life is, in part, an experience of suffering and loss and pain," Ayers writes in Teaching with Conscience in an Imperfect World: An Invitation, published by the Teacher's College Press at Columbia University this year. "But our living experience also embraces other inescapable facts: that we are all in this together, and that much (but not all) of what we suffer in life is...