Logic

The Raven Paradox Is a Confusing Philosophical Conundrum

If you're trying to prove that all ravens are black, a black raven can obviously help your cause. The things is, so can a green apple. Why?

The Raven Paradox

Let's say you're trying to support a simple statement: "All ravens are black." So far, so good, right?

Well, if that's true, then this is also true: "Everything that isn't black isn't a raven."

Now you have two statements you could prove, each of which leads to the same conclusion. You can support the first statement with some pretty intuitive evidence: a black raven — or even better, a lot of them. You can support the second statement with some really random stuff, though: a green apple, for instance (not black, not a raven!), or a school bus, or even a Smurf.

This is the raven paradox, first introduced by the logician Carl Gustav Hempel in the 1940s. It's a seeming philosophical paradox that looks at how conclusions can be confirmed by positive instances. Why does a green apple support the statement "All ravens are black," when it has so little to do with ravens?

Is This Really a Paradox?

If so, it's a big deal. Though the raven example is almost absurdly simple, the paradox itself highlights a potential issue with the scientific method. Does every piece of evidence — even a piece of evidence unrelated to your topic (e.g. ravens) — really support your hypothesis, just because it doesn't contradict it? Is the scientific method taking us into fallacious territory?

Ravens have little bearing on our daily life, and their color even less, but a glitch in the scientific method would, indeed, be a big deal. The scientific method is used to test much higher-stakes hypotheses, like, you know, "This drug cures cancer" and "Global temperatures are rising."

Ultimately, though, many (including Hempel himself) argue the raven paradox isn't so paradoxical. Though it doesn't jibe with our intuition that a green apple would have bearing on raven's hue, that's a problem with our intuition. A green apple does provide an almost imperceptible grain of support for the "All ravens are black" hypothesis. A black raven just provides ... a lot more.

The Paradox of the Ravens

Can you follow what Hempel is saying?

Written by Curiosity Staff October 26, 2016