Taken together, Dark Energy and Dark Matter account for roughly 95% of all there is in the known universe: everything we experience in this material world of ours, every star and galaxy we can see even with our biggest telescopes, is just the tiny less-than-5% bit leftover. A mind-numbing statistic, and one that reminds us just how much we don’t know. Doubt and Uncertainty constantly surround us.
One fairly big assumption underlying the musings of the last two days is that the universe is in fact a rational place. When astronomers stare at distant galaxies, or when physicists collide subatomic particles together, they do so in the belief that the natural world at all levels from the smallest to the largest is amenable to reason: it can be investigated, it can be organised into categories, it can be explained. Without this assumption, science just would not be able to function. But the mystery of Dark Energy and Dark Matter reminds us that science still has a long way to go, and that even the most rigorously evidence-based projects cannot come up with final, definitive answers. It’s all an approximation until something better comes along.
If the men in lab coats are struggling for certainty, what hope is there for us non-specialists who advocate an Evidence-Based approach to life? Do we ever really have enough evidence to be certain about anything?
If we stick to our beliefs and defend them we should at least do so because we are confident that those beliefs have a rational basis, even if we must always add the proviso: so far as the evidence allows. If I want to help prevent Climate Change, or if I am doubtful about the effectiveness of homeopathic medicine, I do so in the belief that I have good reasons for acting in this way. In other words, I think the available evidence is strong enough to support my belief. But how strong is strong enough? In many cases evidence has an annoying habit of being less-than-robust, equivocal, or even downright confusing. What to do?
Here’s just one example: I don’t believe there is any such thing as survival of consciousness after death; and I happen to think I have some decent reasons for holding this belief. Lots of people (probably most people in fact) strongly disagree with me. My reasons can be gleaned by re-reading Day One and Day Two. Here’s a summary: I think that our current (however limited and imperfect) scientific understanding of nature tells us that everything in the universe is made from the same basic building blocks, that we humans occupy no special position in the natural world, that whatever our consciousness is, it is not anything magical or supernatural. All the empirical evidence we have of death tells us that it is a state in which our bodies cease to function and all signs of consciousness disappear from the body. And as I think that consciousness is a bodily state, I feel this adds up to the conclusion that consciousness ceases with the death of the body.
Very many people will find this line of reasoning entirely unconvincing. For them, consciousness is fundamentally mysterious and always will be; humans really are a special case with a unique attribute (a “soul” perhaps) not found elsewhere in nature; the universe is not the rational, knowable place I think it is anyway. Whatever I have to say about science and evidence is irrelevant, since by definition the supernatural is a separate realm, either currently or perhaps permanently immune to the probing of our scientific instruments.
As Day Two was at pains to point out, we really ought to be prepared to modify our beliefs based on new evidence. And evidence is rarely 100% conclusive anyway. Hence, I won’t claim that my belief is somehow watertight and immutable. If reliable, verifiable evidence that our consciousness survives the death of our bodies becomes widely accepted by reputable authorities (let’s say, for example, bodies such as the Royal Society, the UK’s national academy of science) then it would be irrational of me to refuse to accept it. Maybe that evidence will be found one day; so far, I don’t think it has.
Partly, then, my belief rests on a negative assumption: the absence of evidence to justify alternative conclusions. But, as the famous dictum has it, absence of evidence is not evidence of absence, so I cannot disprove any contrary claims: perhaps Heaven or Valhalla really do exist, perhaps we are all sparks destined to reabsorbed into the great cosmic fire from whence we originated, perhaps Spliggug the Ever-Unguent will sneeze his immortal beneficence upon us and we will live forever wrapped in his comforting handkerchief. Who knows which of these is correct? A bit like Dark Matter, mysterious Doubt surrounds this topic
But, to reiterate the conclusion of Day Two, I want to ground my beliefs on the very best evidence I can find, even while admitting that this evidence may be limited and incomplete and subject to revision in the future. Currently I cannot find satisfactory evidence for Valhalla, Spliggug’s handkerchief, or indeed any other form of post-death survival of consciousness. Which is not to say any or all of them are illusory or impossible. But I do hold that before accepting any belief as valid I would like to be confident that I have the strongest possible evidence for it.
To believers in the survival of consciousness after death all of the above is just me missing the point. I am narrow-minded, they will say, my insistence on empirical evidence is simply a refusal to open myself to more spiritual dimensions. My problem with such a line of thinking is this: which spiritual dimensions do you mean, specifically? The ones where the gods of Olympus live, where Odin reigns in Valhalla, where Spliggug sneezes into his magic handkerchief, all or none of these? The problem with holding a belief based on no evidence is not that it cannot be challenged or falsified (it can’t by the way), but rather that we are also forced to accept any and every other belief held by anyone at all as equally valid: if I have an irrational belief (i.e. one not supported by evidence or reasonable arguments) then I have no grounds for disputing any other belief, no matter how patently crazy, dangerous or downright stupid. Believers in the spiritual have no rational way of deciding among themselves which particular version of an afterlife is in fact the right one. Without evidence it all comes down to personal prejudice: I’m a Christian, so I believe in Heaven; I’m a Buddhist so I believe in reincarnation; I’m a vaguely “Spiritual” person so I think whatever feels nice and right to me.
To live a Life According to Evidence is to live without such comforting prejudices; it is a refusal to believe things just because they feel nice; it is being open-minded enough to embrace doubt and uncertainty as inescapable. It is, I believe, a fairer method. Instead of bluntly asserting “I believe X simply because I like the idea”, it challenges us to find good, independent reasons for holding our beliefs. What it does not do is provide any guarantees that we are going to be right. Doubt remains, and we remain ever-vigilant for contrary evidence that will require us to revise our beliefs.
Sometimes when evidence is equivocal we do not always have to decide. Sometimes a plurality of explanations explain the observed phenomena equally well and there is little to choose between them. This is currently the case for Dark Energy and Dark Matter, where a variety of rival hypotheses exist and physicists are competing among themselves to narrow down the options. No one as yet is claiming to have found a satisfactory answer. But it is important to note that our rational approach – for example, our confidence that the universe is knowable and fundamentally explicable by the scientific method – can and should make us reasonably confident that whatever Dark Matter and Dark Energy are, they are not supernatural. Just because we suspend our belief does not therefore require us to admit that any explanation is fair game, no matter how outlandish (“Dark Matter is the souls of dead people floating about in space”). When we confess to ignorance, or when we admit that a multiplicity of probable explanations equally well account for the available evidence, we do so on rational grounds even if – as in the case of the mystery of human consciousness – a final definitive answer may never be reached.
One more example: I really want to believe that there is intelligent life elsewhere in the universe. It’s an inspiring thought that somewhere else other beings are gazing up with curiosity and wonder at an alien sky. But what empirical evidence do we have for this? Precisely none at all. So far, and however much I don’t like to admit it, I have no good grounds for asserting that there are such alien beings. Certainly, I can employ reasonable arguments based on various assumptions about how likely life is to arise elsewhere (the Drake Equation being one) and I might be able to make a rational a priori case to support the hypothesis, but it would be contrary to the Life Lived According to Evidence to make any positive assertion. I hope it is true, I would love it to be true, but if asked do I believe there is intelligent life elsewhere in the universe, I am required to reply: reluctantly, no I don’t. Absence of evidence is not evidence of absence, so I certainly won’t rule out the possibility. (In the meantime, I’m keeping my fingers crossed that some tangible evidence will be forthcoming to allow me to change my answer.)
If absolute certainty is your goal, this evidential insistence is not the path for you. When we live a Life According to Evidence our beliefs will remain unsettlingly fluid and ever subject to provisos, caveats, and amendments. We will often have to suspend judgement, confess that we simply don’t know, or admit that a variety of possible explanations are equally valid. It’s not going to be easy or always comfortable. Why do it then? Because, in the end, this kind of unflinching self-evaluation is good for us all. I think that the very best assurance we can have that we are doing the right thing, acting in the best possible way, contributing to our own and society’s well-being, is to be secure in the knowledge that our beliefs – and therefore our behaviours – are based on the best available evidence.
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Epicurus: Letter to Pythocles
“Whenever we admit one explanation but reject another that agrees equally well with the evidence, it is clear that we fall short in every way of true scientific enquiry and resort instead to myth.”
“There is nothing in heavenly phenomena to contradict these explanations if we always keep in mind the method of multiple causes and make a comprehensive survey of hypotheses and causes consistent with the evidence, without looking to inconsistent explanations and granting them credibility without basis.”
“There are several other methods by which a man may arrive at these observations if he always keeps a firm hold on the evidence and can establish a theory in accordance with this.”
“Thunderbolts may be produced in several ways. Only let mythical explanations not be admitted, and they will not be, if we make inferences about the unseen by attending closely to the visible.”
“To assign a single cause to these occurrences, when the evidence we see demands a number of them, is madness and is properly practised by those who are fanatically devoted to the idle notions of astrology.”
“And there are other explanations of these phenomena that are free from superstition.”
“Keep all these things in mind, Pythocles, for by so doing you will keep yourself free of superstition and be able to understand phenomena akin to these things I have told you about.”