I am visiting the Santa Fe Institute, where everyone who?s anyone is interested in applying the quantitative methods of physics to complex phenomena that aren?t easily reduced to simple theories, and especially to social phenomena ? cities, organizations, bureaucracies, wars, etc.

One of the things that people regularly mention here is the notion that there are regularities in biological and social evolution and phenomena; that you can make predictions over periods of time during which things evolve in a regular way, but that these regularities are punctuated by ?accidents? which occur by chance and thereby defy prediction.

But, I keep wondering: WTF is an accident? WTF is chance?

Prior to quantum  mechanics, in the late 1800s, when physicists had a Lagrangian view of the world, they were obliged to believe that, given initial positions and velocities of all the universe?s particles, the future was IN PRINCIPLE determined. There were really no accidents, even if you couldn?t actually compute the future of everything accurately because of the chaotic behavior of dynamical systems. 

So, unless you believed in free will for at least some living things, then, if someone squeezed you you would have had to agree that everything unfolded deterministically.

Nowadays you can appeal to free will or quantum mechanics, though in the latter case there is still the problem of what causes the wave function to collapse.

So, what is an accident? Is it something we don?t understand causally and is therefore technically unpredictable but in fact causal, or is it something truly random? I can understand a random distribution, but is there such a thing as a random event?

I think what people mean by an accident in this context is a situation where a system causally ends up in an intermediate state that looks a lot like  all the other states the system might have ended up in, but that particular intermediate state in fact has very different future causal consequences from all the apparently more or less similar states it resembles. Hence, for example, the anthropic principle.

I don?t know if I believe in these kinds of accidents. It takes a lot of faith.