  The prescriptions of our two most prominent strands of decision theory,
evidential and causal, differ in a general class of problems known as Newcomb
problems. In these, evidential decision theory prescribes choosing a dominated
act. Attempts have been made at reconciling the two theories by relying on
additional requirements such as ratification (Jeffrey 1983) or "tickles" (Eells
1982). It has been argued that such attempts have failed (Lewis 1981a; Skyrms
1982). More recently, Huttegger (forthcoming) has developed a version of
deliberative decision theory that reconciles the prescriptions of the
evidentialist and causalist. In this paper, I extend this framework to problems
characterised by decision instability, and show that it cannot deliver a
resolute answer under a plausible specification of the tickle. I prove that
there exists a robust method of determining whether the specification of the
tickle matters for all two-state, two-act problems whose payoff tables exhibit
some basic mathematical relationships. One upshot is that we have a principled
way of knowing ex-ante whether a reconciliation of evidential and causal
decision theory is plausible for a wide range of decision problems under this
framework. Another upshot is that the tickle approach needs further work to
achieve full reconciliation.
