Scientists aren’t always certain how the world works, but they are willing to change their minds in the face of evidence.
Science is a process that builds upon existing theories and knowledge by continuously revising them. Every aspect of scientific knowledge can be questioned, including the general rules of thinking that appear to be most certain. So why is science trustworthy if it is always changing? If tomorrow we will no longer see the world as Newton or Einstein found it to be, why should we take seriously today’s scientific description of the world?
The answer is simple: Because at any given moment of our history, this description of the world is the best we have. The fact that it can be improved does not diminish the fact that it is a useful instrument for understanding the world. No one throws away a knife because they think that, someday, a sharper knife must exist.
Consider a folk healer’s herbal medicine. Can we say this treatment is “scientific”? Yes, if it is proven to be effective, even if we have no idea why it works. In fact, several common medications used today have their origin in folk treatments, and we are still not sure how they work. This does not imply that folk treatments are generally effective. To the contrary, most of them are not. What distinguishes scientific medicine from nonscientific medicine is the readiness to seriously test a treatment and to be ready to change our minds if something is shown not to work.
Exaggerating a bit, one could say that the core of modern medicine is not much more than the accurate testing of treatments. A homeopathic doctor is not interested in rigorously testing his remedies: He continues to administer the same remedy even if a statistical analysis shows that the remedy is ineffective. He prefers to stick to his theory. A research doctor in a modern hospital, on the contrary, must be ready to change his theory if a more effective way of understanding illness, or treating it, becomes available.
Misunderstandings of this argument feed much of today’s anti-scientific thinking. Creationist attacks against Darwinism, for instance, often argue that scientists aren’t sure of their own theories because their ideas about evolution are still being revised. But there is a difference between declaring a theory definitive and stating that one theory is better than another. I do not know if this horse is the fastest animal in the world, but I am sure it runs faster than that donkey. Darwin’s ideas might not exhaust everything knowable about the history of life – they likely don’t – but they are far closer to reality than biblical creationism. This we do know for sure.
What makes modern science uniquely powerful is its refusal to believe that it already possesses ultimate truth. The reliability of science is based not on certainty but on a radical lack of certainty. As John Stuart Mill wrote in “On Liberty” in 1859, “The beliefs which we have most warrant for, have no safeguard to rest on, but a standing invitation to the whole world to prove them unfounded.”
In this sense, scientific thinking is not so different from everyday thinking. It is the same activity carried out with more refined instruments. When I arrive in a new city, my idea of its layout is approximate at first. I make for myself a simple mental scheme that allows me to get about as much as I need to. If I live in the city, my mental image will grow richer, and I may realize that some of my first ideas were mistaken. Still, knowing that I may have a better mental map in the future doesn’t diminish the value of the one that sums up what I know right now. In this universe, humanity is like a foreigner just arrived in a new city: We have grasped the basics of how to get around, but there is still so much to learn.
Realizing that knowledge is provisional moves us further and further away from the dream of so many philosophers: finding a foundation to knowledge that can offer certainty. In the 17th century, the English philosopher John Locke grounded the reliability of knowledge in empirical observation, while the French thinker René Descartes relied on the solidity of “pure” reason. Both ways of thinking helped open the doors to modernity by freeing knowledge from the prison of tradition.
But today we have learned that while observation and reason are our best tools toward knowledge, neither guarantees certainty. There are no “pure” facts, observations or empirical data upon which to base theoretical constructions, because our perceptions are heavily structured by our brains, habits of thought, prejudices and theories. Nor is there a purely rational procedure of thinking that can grant certainty, because we are never truly able to reset to zero the tangle of our assumptions. If we attempted to do this, we would no longer be able to think.
The entire history of knowledge has shown us that the world is not as it immediately appears to our eyes. Beyond the plain blue sky there is an immense space full of galaxies, black holes and neutron stars. The uncertainty of our knowledge and the variability of scientific pictures of the world tell us that we have not achieved an ultimate picture of reality. Reality is not the content of our thinking; in fact, it often proves to be quite different from the content of our thinking.
There is no secure method for avoiding error. Our point of departure is always just the ramshackle, error-filled totality of what we think we know. But uncertainty does not make knowledge worthless. If our theory is contradicted by experiment, this remains a real fact, solid as rock, even if we don’t yet know with clarity where our mistake lies. The fact that the assumptions in our reasoning can be mistaken doesn’t change the fact that scientific reasoning is our best cognitive tool.
excerpted from “The Best Reason To Trust Science” by Carlo Rovelli, published in the Wall Street Journal, 9 March, 2023