 How one assesses the legitimacy, plausibility, or likelihood of the specific counter-explanation will bear substantial weight here, and that in turn will depend significantly on among other things background beliefs, commitments, metaphysical dispositions, and the like. If one has a prior commitment to some key α (e.g., to theism, atheism, naturalism, determinism, materialism, or teleology), or assigns a high prior to that α, the plausibility of taking the proposed (new) explanation as undercutting, defeating, or refuting α (and/or Σ) will be deeply affected, at least initially.