I think the inductive argument just isn’t that strong, when dealing with real agents. If, for whatever reason, you believe that your counterpart will respond in a tit-for-tat manner even in a finite-round PD, even if that’s not a Nash equilibrium strategy, your best response is not necessarily to defect. So CDT in a vacuum doesn’t prescribe always-defect, you need assumptions about the players’ beliefs, and I think the assumption of Nash equilibrium or common knowledge of backward induction + iterated deletion of dominated strategies is questionable.
Also, of course, CDT agents can use conditional commitment + coordination devices.
the whole problem with TDT-ish arguments is that we have very little principled foundation of how to reason when two actors are quite imperfect decision-theoretic copies of each other
I think the inductive argument just isn’t that strong, when dealing with real agents. If, for whatever reason, you believe that your counterpart will respond in a tit-for-tat manner even in a finite-round PD, even if that’s not a Nash equilibrium strategy, your best response is not necessarily to defect. So CDT in a vacuum doesn’t prescribe always-defect, you need assumptions about the players’ beliefs, and I think the assumption of Nash equilibrium or common knowledge of backward induction + iterated deletion of dominated strategies is questionable.
Also, of course, CDT agents can use conditional commitment + coordination devices.
Agreed!