DeLong on the Symmetry Argument

Brad DeLong has an excellent post on the prisoner’s dilemma, the symmetry argument and Newcomb’s problem.  He hits the nail on the head with this:

I am a dominant-strategy guy. If you find the Symmetry Argument
convincing–well, Grasshopper, you have once again failed to snatch the pebble
from my hand. But I feel the force of the other side: If you find the Symmetry
Argument an obvious fallacy–well, Grasshopper, you have once again failed to
snatch the pebble from my hand.