Not even wrong

It is comforting that the finest minds in science are as prone as the rest of us to bitching. But the theoretical physicist Wolfgang Pauli (1900-1958) is in a category of his own: the withering comment for which he's best known combines utter contempt on the one hand with philosophical profundity on the other. "This isn't right," Pauli is supposed to have said of a student's physics paper. "It's not even wrong."

"Not even wrong" is enjoying a resurgence as the put-down of choice for questionable science: it's been used to condemn everything from string theory, via homeopathy, to intelligent design. There's a reason for this: Pauli's insult slices to the heart of what distinguishes good science from bad.

"I use 'not even wrong' to refer to things that are so speculative that there would be no way ever to know whether they're right or wrong," says Peter Woit, a mathematician at Columbia University who runs the weblog Not Even Wrong (

This is the principle of falsifiability, famously associated with the philosopher Karl Popper. Hypotheses that might be wrong are the lifeblood of science: you test them, find evidence to support or undermine them, and learn something in the process. But hypotheses that can't even be wrong, Popper maintained, can't tell you anything.

Popper went further. Knowledge only progresses, he argued, when falsifiable claims about the world get proven wrong. In his classic example, you can never confirm the statement "all swans are white", because there might always be some non-white swans you haven't seen yet. But it only takes one black swan to falsify the claim definitively. At that point, you really know something for certain: not all swans are white.

Controversially, Woit thinks the unfalsifiability charge can be levelled at string theory, the branch of physics that claims everything is made up of vibrating strings of energy. Physics, Woit and others argue, has been a victim of its own success: it's getting ever harder to come up with revolutionary new ideas, so ambitious young scientists are forced to make ever wilder speculations. It would be all right if their speculations turned out to be incorrect. It's when they couldn't even hypothetically be incorrect that the problem arises. "There's a class of things that people are working on," Woit says, "where you just have no hope of ever being able to tell."