If you have the time and the patience to read small texts, then go for this one.
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Once upon a time, people used to believe if you studied the components of a system, you could explain everything about it. If you studied atoms, you could explain everything about complex molecules; if you studied complex molecules you could understand cells; if you studied cells you could understand organisms; if you studied how individual organisms behaved you could understand populations. Then quantum mechanics came along and started revealing cracks in such reductionist approaches, and complexity further opened the cracks into gaping holes. Large systems often behave in ways that are not predictable from their components; nothing about the shape of a water molecule predicts thunderclouds. Likewise, applications from statistical physics to social sciences have suggested that the study of large numbers can often model the behavior of markets and social systems better than the study of human nature. This is the primary topic of Critical Mass.
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