I tremble for our world, where, in the smallest ways, we find it impossible, as Marshall Hodgson enjoined, to find room for the other in our minds. If we cannot accommodate a viewpoint in a friend without resorting to unkindness, how can we hope to heal the terrible problems of our planet? I no longer think that any principle or opinion is worth anything if it makes you unkind or intolerant.
Freedom of mind is the real freedom. A person whose mind is not free though he may not be in chains, is a slave, not a free man. One whose mind is not free, though he may not be in prison, is a prisoner and not a free man. One whose mind is not free though alive, is no better than dead. Freedom of mind is the proof of one's existence.
It is to be emphasized that no matter how many [amplitude] arrows we draw, add, or multiply, our objective is to calculate a single final arrow for the event. Mistakes are often made by physics students at first because they do not keep this important point in mind. They work for so long analyzing events involving a single photon that they begin to think that the arrow is somehow associated with the photon [rather than with the event].