Five hundred-odd years ago, in the time of Leonardo da Vinci, a scientist—a term then unknown—was a person of many parts, someone who might work in fields ranging from chemistry to botany, astronomy to metallurgy, to divine the hidden order of the universe.

Even as recently as the early Victorian idea, writes British science historian Peter Watson in his new book Convergence: The Idea at the Heart of Science, the idea that intellectual life was unitary and had a single aim “was regarded as a form of the sublime.” Then, about the time the notion of the scientist came into being, the scientific disciplines began to split into fields. Chemists did chemistry, botanists botany; geologists looked at rocks and agronomists at soil, and they stopped talking to each other.

Now, says Watson, we are entering a new era, one in which the sciences again communicate across disciplinary lines to ask big questions. “Look at two big ideas that came about not exactly simultaneously but in the same decade,” he says, “namely the conservation of energy and natural selection. They and other ideas were long considered apart from each other. But now the sciences are increasingly overlapping and increasingly telling the same story in the same way that you have a photograph of a particular object taken from different angles: the image is slightly different in each case, but it adds up to a whole. The result of that, in these converging sciences, is that we have an ever clearer picture of the universe and how it works.”

These big-picture questions include such thorny problems as the origin of life in the universe. How did inanimate matter become animate? To answer that, biologists have increasingly borrowed from quantum physics, two dauntingly different disciplines; they have not necessarily become physicists as such, but they think using some of the same tools. It’s for this reason, Watson believes, that a few years down the line we’ll be seeing the most interesting work coming not out of traditional science departments at the big universities but instead from multidisciplinary research centers such as the Max Planck Institutes of Germany, a model that is becoming more established in the U.S. and Britain.

As the sciences converge, Watson writes, some of the “softer” ones, such as the social sciences of psychology and economics, are acquiring a harder edge, backed by rigorous methods and plenty of data. Psychology, he notes, “was once really a kind of philosophical activity, but now it involves lots of physics and studies of the chemistry of the brain.” Psychology, he notes, is converging with those sciences, and with economics as well, which in turn is converging with it and other sciences.

In one extended example, he considers the ever growing body of work surrounding the problem of economic inequality, all of which may be leading to the conclusion that it is simply an inevitable consequence of so-called free market capitalism that some people are rich and some poor. Even so, Watson adds, we can use the sciences to predict how wealth will expand and contract, who will gain and who will be left out—a kind of social Darwinism with big numbers to back it. “It’s up to the economists to prove all this,” he says, “but then we can use the same data to rethink how we treat problems of poverty, apply aid, and so forth. As Niels Bohr said, every problem contains its solution, so if we accept that inequality is inevitable, it doesn’t mean that we have to accept that conditions can’t be improved.”

Where does one discipline end and another begin? By Watson’s account, that’s not really an operative question anymore. Just as we’re in a golden age of science, we’re also in a golden age of writing about science, and Convergence leads us into fascinating new territory.

Gregory McNamee is a contributing editor.