Should a scientist have "faith"?

But there’s a method to the madness here. First consider what faith is typically defined as – it is belief in the absence of evidence. Now consider what science is in its purest form. It is a leap into the unknown, an extrapolation of what is into what can be. Breakthroughs in science by definition happen “on the edge” of the known. Now what sits on this edge? Not the kind of hard evidence that is so incontrovertible as to dispel any and all questions. On the edge of the known, the data is always wanting, the evidence always lacking, even if not absent. On the edge of the known you have wisps of signal in a sea of noise, tantalizing hints of what may be, with never enough statistical significance to nail down a theory or idea. At the very least, the transition from “no evidence” to “evidence” lies on a continuum. In the absence of good evidence, what does a scientist do? He or she believes. He or she has faith that things will work out. Some call it a sixth sense. Some call it intuition. But “faith” fits the bill equally.

If this reliance on faith seems like heresy, perhaps it’s reassuring to know that such heresies were committed by many of the greatest scientists of all time. All major discoveries, when they are made, at first rely on small pieces of data that are loosely held. A good example comes from the development of theories of atomic structure.

When Johannes Balmer came up with his formula for explaining the spectral lines of hydrogen, he based his equation on only four lines that were measured with accuracy by Anders Ångström. He then took a leap of faith and came up with a simple numerical formula that predicted many other lines emanating from the hydrogen atom and not just four. But the greatest leap of faith based on Balmer’s formula was taken by Niels Bohr. In fact Bohr did not even hesitate to call it anything but a leap of faith. In his case, the leap of faith involved assuming that electrons in atoms only occupy certain discrete energy states, and that figuring out the transitions between these states somehow involved Planck’s constant in an important way. When Bohr could reproduce Balmer’s formula based on this great insight, he knew he was on the right track, and physics would never be the same. One leap of faith built on another.

To a 21st century scientist, Bohr’s and Balmer’s thinking as well as that of many other major scientists well through the 20th century indicates a manifestly odd feature in addition to leaps of faith – an absence of what we call statistical significance or validation. As noted above, Balmer used only four data points to come up with his formula, and Bohr not too many more. Yet both were spectacularly right. Isn’t it odd, from the standpoint of an age that holds statistical validation sacrosanct, to have these great scientists make their leaps of faith based on paltry evidence, “small data” if you will? But that in fact is the whole point about scientific belief, that it originates precisely when there isn’t copious evidence to nail the fact, when you are still on shaky ground and working at the fringe. But this belief also supremely echoes a famous quote by Bohr’s mentor Rutherford – “If your experiment needs statistics, you ought to have done a better experiment.” Resounding words from the greatest experimental physicist of the 20th century whose own experiments were so carefully chosen that he could deduce from them extraordinary truths about the structure of matter based on a few good data points.

The transition between belief and fact in science in fact lies on a continuum. There are very few cases where a scientist goes overnight from a state of “belief” to one of “knowledge”. In reality, as evidence builds up, the scientist becomes more and more confident until there are not enough grounds for believing otherwise. In many cases the scientist may not even be alive to see his or her theory confirmed in all its glory: even the Newtonian model of the solar system took until the middle of the 19th century to be fully validated, more than a hundred years after Newton’s death.

A good example of this gradual transition of a scientific theory from belief to confident espousal is provided by the way Charles Darwin’s theory of evolution by natural selection, well, evolved. It’s worth remembering that Darwin took more than twenty years to build up his theory after coming home from his voyage on the HMS Beagle in 1836. At first he only had hints of an idea based on extensive and yet uncatalogued and disconnected observations of flora and fauna from around the world. Some of the evidence he had documented – the names of Galapagos finches, for instance – was wrong and had to be corrected by his friends and associates. It was only by arduous experimentation and cataloging that Darwin – a famously cautious man – was able to reach the kind of certainty that prompted him to finally publish his magnum opus, Origin of Species, in 1859, and even then only after he was threatened to be scooped by Alfred Russell Wallace. There can be said to be no one fixed eureka moment when Darwin could say that he had transitioned from “believing” in evolution by natural selection to “knowing” that evolution by natural selection was true. And yet, by 1859, this most meticulous scientist was clearly confident enough in his theory that he no longer simply believed in it. But it certainly started out that way. The same uncertain transition between belief and knowledge applies to other discoveries. Einstein often talked about his faith in his general theory of relativity before observations of the solar eclipse of 1919 confirmed its major prediction, the bending of starlight by gravity, remarking that if he was wrong it would mean that the good lord had led him down the wrong garden path. When did Watson and Crick go from believing that DNA is a double helix to knowing that it is? When did Alfred Wegener go from believing in plate tectonics to knowing that it was real? In some sense the question is pointless. Scientific knowledge, both individually and collectively, gets cemented with greater confidence over time until the objections simply cannot stand up to the weight of the accumulated evidence.

Faith, at least in one important sense, is thus an important part of the mindset of a scientist. So why should scientists not nod in assent if someone then tells them that there is no difference, at least in principle, between their faith and religious faith? For two important reasons. Firstly, the “belief” that a scientist has is still based on physical and not supernatural evidence, even if all the evidence may not yet be there. What scientists call faith is still based on data and experiments, not mystic visions and pronouncements from a holy book. More importantly, unlike religious belief, scientific belief can wax and wane with the evidence; it importantly is tentative and always subject to change. Any good scientist who believes X will be ready to let go of their belief in X if strong evidence to the contrary presents itself. That is in fact the main difference between scientists on one hand and clergymen and politicians on the other; as Carl Sagan once asked, when was the last time you heard either of the latter say, “You know, that’s a really good counterargument. Maybe what I am saying is not true after all.”

Faith may also interestingly underlie one of the classic features of great science – serendipity. Unlike what we often believe, serendipity does not always refer to pure unplanned accident but to deliberately planned accident; as Alexander Fleming memorably put it, chance favors the “prepared mind”. A remarkable example of deliberate serendipity comes from an anecdote about his discovery of slow neutrons that Enrico Fermi narrated to Subrahmanyan Chandrasekhar. Slow neutrons unlocked the door to nuclear power and the atomic age. Fermi told Chandrasekhar how he came to make this discovery which he personally considered – among a dozen seminal ones – to be his most important one (From Mehra and Rechenberg, “The Historical Development of Quantum Theory, Vol. 6”):

Chandrasekhar’s invocation of Hadamard’s thesis of unconscious discovery might provide a rational underpinning for what we are calling faith. In this case, Fermi’s great intuitive jump, his seemingly irrational faith that paraffin might slow down neutrons, might have been grounded in the extensive body of knowledge about physics that was housed in his brain, forming connections that he wasn’t even aware of. Not every leap of faith can be explained this way, but some can. In this sense a scientist’s faith, unlike religious faith, is very much rational and based on known facts.

Ultimately there’s a supremely important guiding role that faith plays in science. Scientists ignore believing at their own peril. This is because they have to constantly tread the tightrope of skepticism and wonder. Shut off your belief valve completely and you will never believe anything until there is five-sigma statistical significance for it. Promising avenues of inquiry that are nonetheless on shaky grounds for the moment will be dismissed by you. You may never be the first explorer into rich new scientific territory. But open the belief valve completely and you will have the opposite problem. You may believe anything based on the flimsiest of evidence, opening the door to crackpots and charlatans of all kinds. So where do you draw the line?

In my mind there are a few logical rules of thumb that might help a scientist to mark out territories of non-belief from ones where leaps of faith might be warranted. In my mind, plausibility based on the known laws of science should play a big role. For instance, belief in homeopathy would be mistaken based on the most elementary principles of physics and chemistry, including the laws of mass action and dose response. But what about belief in extraterrestrial intelligence? There the situation is different. Based on our understanding of the laws of quantum theory, stellar evolution and biological evolution, there is no reason to believe that life could not have arisen on another planet somewhere in the universe. In this sense, belief in extraterrestrial intelligence is justified belief, even if we don’t have a single example of life existing anywhere else. We should keep on looking. Faith in science is also more justified when there is a scientific crisis. In a crisis you are on desperate grounds anyway, so postulating ideas that aren’t entirely based on good evidence isn’t going to make matters worse and are more likely to lead into novel territory. Planck’s desperate assumption that energy only comes in discrete packets was partly an act of faith that resolved a crisis in classical physics.

Ultimately, though, drawing a firm line is always hard, especially for topics on the fuzzy boundary. Extra-sensory perception, the deep hot biosphere and a viral cause for mad cow disease are three theories which are implausible although not impossible in principle; there is little in them that flies against the basic laws of science. The scientists who believe in these theories are sticking their necks out and taking a stand. They are heretics who are taking the risk of being called fools; since most bold new ideas in science are usually wrong, they often will be. But they are setting an august precedent.

If science is defined as the quest into the unknown, a foray into the fundamentally new and untested, it is more important than ever especially in this age of conformity, for belief in science to play a more central role in the practice of science. The biggest scientists in history have always been ones who took leaps of faith, whether it was Bohr with his quantum atom, Einstein with his thought experiments or Noether with her deep feeling for the relationship between symmetry and conservation laws, a feeling felt but not seen. For creating minds like these, we need to nurture an environment that not just allows but actively encourages scientists, especially young ones, to tread the boundary between evidence and speculation with aplomb, to exercise their rational faith with abandon. Marie Curie once said, “Now is the time to fear less, so that we may understand more.” To which I may add, “Now is the time to believe more, so that we may understand even more.”

First published on 3 Quarks Daily