Men, it has been well said, think in herds; it will be seen that they go mad in herds, while they only recover their senses slowly, and one by one.
Charles Mackay

Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so.
Douglas Adams

Man is the only animal that laughs and weeps, for he is the only animal that is struck with the difference between what things are and what they ought to be.
William Hazlitt