have tried to prove him wrong: Humboldt, Thompson, Max Rubner, Alfred Lotka, Ludwig von Bertalanffy, Evelyn Hutchinson, and Robert MacArthur, the modern generation of macroecologists and their physicist colleagues. Many have invoked Newtonian science as their model and goal, and many have sought to go beyond a single blade of grass to find and explain patterns in the living world that encompass the whole planet.

No one now disputes that plants, animals, rocks, and galaxies are made from the same stuff and are subject to the same physical laws. This fact has become trivial. What is not trivial is whether we can find general laws, similar to those that physics applies to particles and planets, which explain how the living world works.

Of course, biology already has one all-pervading principle. When Kant invoked Newton, he was arguing that the world only made sense “as the product of an intelligent cause.” Biology has already shown, through the theory of evolution, that this is not so. From the facts of genetic mutation, inheritance, and natural selection, evolutionary biology shows us how and why life came to be the way it is.

Many biologists believe that, other than evolution, generality in biology is unlikely. They argue that biological systems are more complex than physical ones. Particles such as electrons and quarks, for example, can be described by their mass, velocity, and electrical charge. Geologists studying the earth’s crust must come to terms with a few thousand types of mineral. But there are millions of species, each differing in size, shape, behavior, habitat, range, and rarity. Within species, every individual is different, and all change over the course of their lives. Hindsight, these scientists argue, might show us how nature as we see it came about, through past events such as drifting continents and changing climates. And on a case-by-case basis, most biologists are confident that we can explain, by looking at factors such as the availability of food, the threat of predators, the fights between males, or what mates females prefer, why a particular species does what it does. But many also think that the interactions between living things and their environment and each other is too complicated, and too dependent on the circumstances of each moment, to allow generalization.

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