I recently finished reading Charles Darwin’s The Origin of Species.

The full title is actually On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life.

It is an extraordinary work. Mostly because it is one of the few scientific pieces of great importance that is immediately accessible to the general reader. One is hard-pressed to read Newton’s epochal Principia, even though it has a helpful diagram on almost every page, because it is mostly a math book. You need scratch paper and a pencil by your side! The same can be said for Copernicus or Kepler. Albert Einstein’s papers from 1905 that established his reputation are short, but dense and obscure. And again the math is a barrier.

Perhaps something like Rachel Carson’s Silent Spring compares, although that is a very brief book and was clearly written for mainstream reception. Darwin was writing to his fellow naturalists. Her book, it could be argued, had a similar impact. Carson’s views have ultimately prevailed among the citizenry, few would argue with her claims today. Darwin, not so much. Anti-evolutionary sentiment is very strong in American education and politics despite its widespread acceptance throughout the world.

The discovery of genetics and the means of inheritance only strengthened Darwin’s (and Alfred Russel Wallace’s) evolutionary schemes. No scientist today questions the idea of the mutability of species. Darwin’s book actually addresses a simple question: does life change over time? Most authorities of Darwin’s time (the book was published in 1859) believed that all living species were specifically created. A species, by definition, was immutable.

The Origin demolishes that point of view. What makes it a great book is that Darwin does it with a scalpel and a smile. The book is not a polemic. It’s a careful, humble, and meticulous exposition of something that became obvious to Darwin over the course of his journeys and studies. He brings the reader along with a clear awareness of the arguments against his ideas and shows how the old ways of thinking just don’t work as well.

That’s the key. Darwin shows, chapter after chapter, how natural selection and variation account for what we actually see in the natural world. It becomes clear that the objections to an evolutionary outlook are grounded in philosophy and religion, not in observation of real things.

The Origin shows a powerful but patient intellect at work. Darwin does not like to leap to conclusions despite his passion for his theory. He takes great pains to support his claims and show how evolution, as a paradigm for the study of life, is more illuminating, more interesting, and more encompassing than the existing modes of thought.

He makes his case. By the end of the book you can see how the new theory supplants the old because it has better explaining power. Reading Darwin helps you understand the scientific method. He starts with the facts: his observations and the results of his experiments; and the mountains of evidence from the work of others. Then, and only then, does he postulate the unifying concepts.

Be suspicious of arguments that start with the principles first. The principles should emerge from the evidence. If you state the theory at the beginning, it will be easy to find examples that support your point of view. If you look first, and then examine what you find, you might have a chance to figure out the big ideas. The first method is biased. The second gives the truth an opening.