A Lantern in the Dark #3


J Lantern

Doubt is one of the principal tools in the Skeptic’s toolbox, but we’re not cynics. We don’t automatically doubt every claim we confront. There are degrees of doubt. If you claim that you went to the movies yesterday, I have no reason to doubt you. Why would anyone lie about such an innocuous occurrence? Furthermore, the truth of your statement doesn’t really affect me in any tangible way. Why should I care if you didn’t go to the movies?

However, the credibility of the source is as important as the claim itself when assessing whether or not doubt is warranted. Maybe you’re a pathological liar. In that case, I have no reason to believe anything you say.

Some claims are extraordinary. Carl Sagan’s dragon is an excellent parable about extraordinary claims. For those that haven’t read The Demon-Haunted World, and I highly recommend that you do, I’ll briefly describe Sagan’s allegory.[1]

The story goes like this: someone (whom I will refer to, for simplicity, as him, though it could just as easily be a her) claims to have a dragon living in his garage. This is a pretty grand claim, indeed! Being skeptical, I say, “Great! Let’s go see it!” He replies, “You can’t. He’s invisible.” I propose scattering flour on the floor in an attempt to see the dragon’s footprints. He assures me that it doesn’t leave footprints because it flies all the time, never touching the ground. I suggest going into the garage and just walking around until we stumble into the dragon, but, I’m thwarted again. It is, I am told, insubstantial and can’t be felt.

On it goes. Every test I propose is defeated by some property that renders the dragon undetectable. I have no reason to believe it exists, since it seems to be indistinguishable from an imaginary dragon. Providing no good evidence, my fictitious friend has failed to meet his burden of proof.

Burden of proof is a contentious issue, especially in religious circles where there is a paucity of good evidence. In general, the person making the claim is responsible for proving the claim true. Oftentimes, people will try to shift the burden of proof to their opponent.

For example, I’ve debated with religious people whom I’ve asked to provide evidence that a god exists. They try to counter by turning the argument around, asking me to provide evidence that we live in a god-free universe.[2] Ignoring the fact that I never claim to know (an important distinction) that we do live in a god-free universe, this is a sophist’s tactic. It tries to leverage the difficulty (some say impossibility) of proving that something doesn’t exist (can you prove that unicorns don’t exist anywhere in the universe?)[3] That the universe exists is objectively true. Whether or not a god abides in, or outside of, the universe is the point in contention. In the absence of sufficient evidence, for or against (as in the case of a god), Occam’s Razor is a useful tool most of us instinctively use to help decide what to believe.[4]

William of Ockham was a 14th century friar who’s eponymous maxim for efficient reasoning was interpreted by Bertrand Russell as follows: “if one can explain a phenomenon without assuming this or that hypothetical entity, there is no ground for assuming it.”[5] In other words, in the absence of sufficient evidence to determine which of two theories (equivalent in all other respects) is true, opt for the one that makes the fewest, or least improbable, assumptions (i.e., is the simplest).

Later, my fictitious dragon keeper’s garage burns to the ground. He comes to me proclaiming that he finally has evidence for the existence of the dragon, since it has used its fire-breath to burn the garage down! Unfortunately for him, I saw a pile of oily rags heaped in the corner of his garage, which are known to spontaneously ignite. My friend has failed again, because, even though I didn’t actually see the rags catch flame, it is the explanation for which the underlying assumptions are most credible.

There are some rather extraordinary claims that do warrant belief. Relativity and quantum mechanics are counterintuitive explanations of motion in space and time. The flow of time isn’t constant? Space can stretch and curve? Particles can be in multiple locations at one time? These theories have been thoroughly tested over the last century and have withstood every challenge. Quantum mechanics is one of our most successful theories in physics. The same can be said for Evolution. Not just well tested, there are many concepts in biology that would be very difficult to explain without Evolution (unless, of course, you believe in an omnipotent deity; then all things are explained—except, of course, the deity). The theories underlying our understanding of climate change are also firmly supported by evidence, to the point that virtually all climate scientists believe climate change is happening, and that it’s caused by human activity.

To be a good Skeptic, you have to carefully balance doubt so as not to become a cynic. Skeptics want to ensure that, as much as possible, the things we believe are true. We want to have an open mind, but not so open that our brains fall out. The more incredible the claim, the more good evidence we will require. What constitutes “good” evidence? That’s a topic for another day.


  1. The Demon-Haunted World – Science as a Candle in the Dark © 1996 by Carl Sagan, pg. 160
  2. William Lane Craig, a Christian apologist and debater, commonly uses a form of this tactic by asking his opponents to provide an argument or evidence to show that “atheism is true.” (For an example, see the transcript of this debate with Christopher Hitchens.) This is only impressive to people who don’t really understand what atheism means.

    Atheism is simply that one finds there is insufficient evidence to justify belief in a deity. Substitute this into Craig’s (paraphrased) request: provide an argument or evidence to show that one finds there is insufficient evidence to justify belief in a deity is true. Now it is readily apparent that Craig’s question is nonsensical. Whether or not one finds the available evidence sufficient to warrant belief is a personal determination. Everyone will have a different threshold. Craig is well aware of this, and uses this blatant casuistry as a cheap ploy to win audience support. In the minds of the spectators, he is asking his opponent to prove there is no god, which they will fail at since a proof is impossible.

  3. See this Wikipedia article and this James Randi video.
  4. See this article for a discussion of the burden of proof.
  5. See http://en.wikipedia.org/wiki/William_of_Ockham