The Importance of Consilience in Science
Science is not a democracy. A consensus of evidence may be interesting, but technically it may not be significant. The thoughts of a majority of scientists doesn’t mean a hill of beans. It’s all about the evidence. The science is never settled.
These are refrains that I and other science communicators have been using over and over again when we turn to analysing debates and discussions based on scientific principles. I think we get torn between remaining true to the philosophical principles by which science is conducted and trying to make those principles familiar to an audience that probably does not understand them.
So let me introduce a concept that is all-too-often overlooked in science discussions, that can actually shed some light deep into the mechanisms of science and explain the anatomy of a scientific debate. It’s the phonically beautiful term ‘consilience’.
Consilience means to use several different lines of inquiry that converge on the same or similar conclusions. The more independent investigations you have that reach the same result, the more confidence you can have that the conclusion is correct. Moreover, if one independent investigation produces a result that is at odds with the consilience of several other investigations, that is an indication that the error is probably in the methods of the adherent investigation, not in the conclusions of the consilience.
Let’s take an example to unpack this concept, an example where I first came across the term and it is a beautiful case of consilience at work. Charles Darwin’s On Origin Of Species is a masterpiece of consilience. Each chapter is a separate line of investigation and, within each chapter there are numerous examples, investigations and experiments that all join together to reach the same conclusion: that life changes through time and that life has evolved on Earth. Take apart On Origin Of Species case by case and no single piece of evidence that Darwin mustered conclusively demonstrates that evolution is true. But add those cases back together and the consilience is clear: evidence from artificial breeding, palaeontology, comparative morphology and a host of other independent lines of investigation combine to confirm the same inescapable conclusion.
That was 1859. Since then yet more investigations have been added to the consilience for evolution. What’s more, these investigations within the biological and geological sciences have been joined with others from physics and chemistry as well as completely new areas of science such as genetics, radiometric dating and molecular biology. Each independent line of investigation builds the consilience that the world and the universe are extremely old and that life has evolved through unfathomable durations of time here on our home planet.
So, when a new line of investigation comes along claiming evidence and conclusions contrary to evolution, how can that be accommodated within the consilience? How does it relate to so many independent strains conjoined by a similar conclusion at odds with the newcomer? Can one piece of evidence overthrow such a huge body of work?
Such is the thinking of those pesky creationists who regularly come up with “Ah-Ha!” and “Gotcha!” factoids that apparently overturn, not just evolution, but the whole consilience of science. Without exception, every single case that has been brought forward over the years does not hold up to scrutiny: the contrary result is in error and thus not really in conflict with the consilience. Depressingly, most of the ‘examples’ that the creationists put forward have been discredited time and time again but they are always willing to try their hand at foisting discredited material on a new, naive audience.
The same can be said of the Climate Change debate. While it has been pointed out many times that this is not an even debate and that the vast majority of climate scientists are in one camp (for example here and here) this by itself is not particularly helpful: science is not a democracy. But what has been underplayed is that the consilience of evidence for anthropogenic climate change is particularly strong. The IPCC reports are a consilience of hundreds of independent lines of evidence all converging on the same or similar conclusions. Supplement that body of work with complementary investigations outside the reports and the consilience builds; we have more confidence that their conclusions are correct. This is then magnified because of the consilience between the investigations within climate science research and the findings of the rest of science. They all point to the same conclusions about how the world works and the climate science is comfortably nested within all the other scientific disciplines.
While researching this article, I found out that the term ‘consilience’ and its basic principles were coined by the polymath William Whewell (1794-1866). He was a truly remarkable man partly because of the breadth of his work taking in philosophy, theology, physics, mineralogy, mathematics, poetry, astronomy, economics, mechanics and others. He also coined many other words besides ‘consilience’ that have entered the scientific and general lexicon. He came up with the word ‘scientist’ as well as ‘physicist’, ‘catastrophism’ and ‘uniformitarianism’ and went on to suggest to Michael Faraday words such as ‘ion’, ‘anode’, ‘cathode’ and ‘dielectric’. Among his many notable associations: while he was a don at Cambridge, he met a young student, Charles Darwin, and later recommended him for the position of secretary for the Geological Society of London. In honour of their enduring friendship, Darwin quoted Whewell on the frontispiece of On Origin Of Species:
“But with regard to the material world, we can at least go so far as this—we can perceive that events are brought about not by insulated interpositions of Divine power, exerted in each particular case, but by the establishment of general laws.”
And thus was born the origin of the great consilience of human endeavour that we call ‘science’.
By Paul Willis (@fossilcrox)
Feature image “Consiliance” generated by RiAus.
Body image 1 “Darwin tree” sourced from Wikimedia Commons and authored by Charles Darwin.
Body image 2 “PSM V07 D008 William Whewell” sourced from Wikimedia Commons.