that people—or, if you like, automata, algorithms—can and do act in situations that are not well defined.

Both are dynamic systems in which the selfish actions of countless individuals—whether they be cells or investors—lead to unpredictable consequences at the system level. In turn, these collective actions and consequences feed back to influence individual actions in endless cycles of adaptation and evolution.

When something happens to the expectation value, is that actually also what happens over a long time to the thing that we are observing?

Markets are therefore called “emergent” systems: prices emerge from all members’ interactions and can’t be observed just by looking at a few.