  As we show by using notions of equilibrium in infinite sequential games,
crashes or financial escalations are rational for economic or environmental
agents, who have a vision of an infinite world. This contradicts a picture of a
self-regulating, wise and pacific economic world. In other words, in this
context, equilibrium is not synonymous of stability. We try to draw, from this
statement, methodological consequences and new ways of thinking, especially in
economic game theory. Among those new paths, coinduction is the basis of our
reasoning in infinite games.
