D’oh, re: the optimum of the objective, I now see that the solution is nontrivial. Here’s my current understanding.
Intuitively, the MAP version of the objective says: find me a simple model theta1 such that there’s more-complex theta2 with high likelihood under p(theta2|theta1) (which corresponds to sampling theta2 near theta1 until theta2 satisfies head-agreement condition) and high data-likelihood p(data|theta2).
And this connects to the previous argument about world models and language as follows: we want theta1 to contain half a world model, and we want theta2 to contain the full world model and high data-likelihood (for one of the head) and the two heads agree. Based on Step1, the problem is still pretty underconstrained, but maybe that’s resolved in Step 2.
D’oh, re: the optimum of the objective, I now see that the solution is nontrivial. Here’s my current understanding.
Intuitively, the MAP version of the objective says: find me a simple model theta1 such that there’s more-complex theta2 with high likelihood under p(theta2|theta1) (which corresponds to sampling theta2 near theta1 until theta2 satisfies head-agreement condition) and high data-likelihood p(data|theta2).
And this connects to the previous argument about world models and language as follows: we want theta1 to contain half a world model, and we want theta2 to contain the full world model and high data-likelihood (for one of the head) and the two heads agree. Based on Step1, the problem is still pretty underconstrained, but maybe that’s resolved in Step 2.