Why do wars and revolutions happen? We do not know. We know only that to produce the one or the other men [sic] form themselves into a certain combination in which all take part; and we say that this is the nature of men [sic], that this is the law" -Leo Tolstoy, War and Peace
"A phase transition is a sudden, global change in behaviour arising from the interactions of many constituent particles" -Philip Ball, Critical Mass: How One Thing Leads to Another