I still owe you Part II of my Darwinism post. But in the meantime, I’d like to pontificate about a fallacy that I’ve seen so often it deserves a name. I’ll call it the But-What-If? Fallacy, after the following joke:
“Let n be an integer…”
“But what if n isn’t an integer?”
The fallacy consists of bringing something up that was specifically defined to be irrelevant. Of course, no one would be silly enough to do that in real life! Except…
- “I would never want to live in a society where people were always happy. Such a society would be a stifling, conformist dystopia, like in Gattaca or Brave New World.”
Well then, people wouldn’t always be happy, would they?
- “If quantum mechanics is nonlinear, then P=NP in the physical world.”
This one makes steam emanate from my ears. Let’s repeat three times: P and NP are purely mathematical concepts. As such, the laws of physics can have no bearing on whether or not they are equal.
(Of course, it could be that PA=NPA where A is a “real world oracle.” But if you understood that point, then you’re already way beyond the “P=NP in the physical world” crowd.)
- “I could never marry a guy I didn’t love, even if he was unfailingly kind, generous, and loyal. I’d never know when he might abandon me.”
- “You shouldn’t take this drug, even if it will help reduce your anxiety. You can reduce your anxiety just as well without it.”
- “Sure, a perfect computer simulation of a human being might hold an intelligent conversation. But could it ever write a poem, or laugh at a joke, or fall in love, or…”
GODDAMMIT! WHAT PART OF “BY ASSUMPTION” DON’T YOU UNDERSTAND?
Sorry, I sometimes get carried away. In the past, my favored solution to the BWI? Fallacy was forcible re-education camps for everyone who commits it. But lately, I’ve come to think that a softer approach might work.
See, the problem is that most people (even theoretical physicists) have very little experience thinking like mathematicians. By nature, people want to keep coming back to the issues they care about, even when you ask them a hypothetical question that defines those issues away. The key is, first, to identify the real question on the other person’s mind:
Are NP-complete problems hard in the physical world?
Is this guy as kind and generous as he seems?
Will this drug really help reduce my anxiety?
Could a computer that writes decent poetry, laughs at jokes, etc. be built?
You can then point out the difference between this question and the one that was asked. Often, the more abstract question won’t even have occurred to the other person. But once the person understands the abstract question — and why it remains, even after the concrete one has been answered — it’s time to extend your hand. “Welcome to the business.”