 Together, 1 and 2 constitute a sort of semantic reductionism: the meaning of any ordinary language expression is reduced to the meanings of the base vocabulary via the epistemic exercise of considering scenarios as actual and worlds as counterfactual. And 3 ensures that this epistemic exercise is an accurate guide to metaphysical possibility. Chalmers’ Core Thesis is meant to capture this tight relationship between grasp of meaning, apriori reflection, and metaphysical possibility.