What's the issue with Solomonoff induction here?

"Higher-order-logic": reputedly down to concerns about uncomputability - which don't seem very interesting to me.

"Anthropic: I figure that can be dealt with in the same way as any other reference machine problem: by "conditioning" it by exposing it to the world.

"Cartesian": I think that's probably to do with this (from E.Y.):

AIXI devises a Cartesian model of a separated environmental theatre, rather than devising a model of a naturalistic reality that includes AIXI.

Fun stuff - but nothing specifically to do with Solomonoff induction. The papers on Orseau's Mortal Universal Agents page address this issue.