It is hardly possible to overstate the value, in the present low state of human improvement, of placing human beings in contact with persons dissimilar to themselves, and with modes of thought and action dissimilar to themselves, and with modes of thought and action unlike those with which they are familiar…. Such communication has always been, and is particularly in the present age, one of the primary sources of progress.
—John Stuart Mill, The Principles of Political Economy: With Some of Their Applications to Social Philosophy, bk v, ch xvii, sec 3 (1848) in: The Collected Works of John Stuart Mill, vol 3, p. 594.
