The Value of Evidence

“A fire-breathing dragon lives in my garage”

“Show me,” you say.

I lead you to my garage. You look inside and see a ladder, empty paint cans, an old tricycle–but no dragon.

“Where’s the dragon?” you ask.

“Oh, she’s right here,” I reply, waving vaguely. “I neglected to mention that she’s an invisible dragon.”

You propose spreading flour on the floor of the garage to capture the dragon’s footprints.

“Good idea,” I say, “but this dragon floats in the air.”

Then you’ll use an infrared sensor to detect the invisible fire.

“Good idea, but the invisible fire is also heatless.”

You’ll spray-paint the dragon and make her visible.

“Good idea, but she’s an incorporeal dragon and the paint won’t stick.”

…

And so on…

I counter every physical test you propose with a special explanation of why it won’t work.

The above is an excerpt from the late Carl Sagan’s book; “A demon haunted world: Science as a Candle in the dark”. The question that must be asked in this instance, what precisely is the difference between an invisible, floating, heatless, intangible dragon and just the empty air of someone’s garage? There isn’t one. Is there a mystical, undetectable fairy sitting on your shoulder right now? It makes absolutely no difference.

There are good reasons and bad reasons to believe a proposition. Although it is not possible to prove or disprove anything to absolute certainty^[1], it is undoubtable that certain descriptions of the world seem more likely to be true than others. Evidence is that which points to the likelihood of a possible state of the world. Imagine you were lying down in your bed, contemplating what to wear for the day. You hear a familiar pitter, patter sound coming from the direction of your window. Without even getting out of bed, you can infer that it is raining. Evidence is the admission that there are patterns to the events that dictate our lives. When x strikes, y tends to follow.

No one made this up. This is merely the natural way we think. When all the signs point toward something being true, we tend to believe it. There are patterns in the universe and we developed over one to two hundred thousand years of hominid evolution to be pattern seeking beings. Some of these patterns are real and some are false, but the dividing line is evidence. Will x reliably lead to y?

To be a functional human being, we have no choice but to be compelled by the forces of reason and evidence^[2]. If one day you notice your house is on fire, you are impelled to believe it. You have no say in the matter. The idea that we choose what we believe is absurd, do we choose what reality is?

Ultimately reason and evidence are values, albeit values that we all tend to hold. If you did not value evidence, what evidence could I provide you to value it? If you did not value reason, what reasons could I provide for you to value it? It is not possible to make someone value reason and evidence, but it is possible to make them realise they already value them. Certain people may claim they they do not share these values, but if you ask them why not and they give you an intelligible answer it proves that they indeed do.

“But Sashin, everything you are saying in this post is obvious?”

A few years ago I had a conversation with one of my friends. It went something like this:

“Certain things are true and certain things are false. If a person was outside and it started raining it would be irrational to think otherwise.”

“Whether or not it is raining is just a point of view”

Now imagine if this person was thrown into an icy lake.

“What do you think you are doing? I’m freezing!”

“That’s just your point of view.”

There is a certain attitude that seems to have poisoned our discourse and that attitude sounds something like this:

“Everyone is right in their own way. Every opinion is valid. No one is really wrong.”

Here the serpent devours its own tail. Is the above sentiment right? Or is it just another point of view? And if it is just another point of view, does that mean it is just as valid as “some things are right and some are wrong”?

If a person claims it is 30^oC outside and another claims it is -100^oC, is one of these claims closer to reality? Or are they both equally true and worthy of respect?

If a person says the Earth is round and another says the Earth is flat, is one of them really more right than the other or are these two equally valid ways of looking at the world?

If a person believes the universe is 13.7 billion years old and another believes it is six thousand years old, is one of them more accurate than the other or are these just two alternative points of view?

Please, think about these things.