Explanatory Internalism and the Limits of Ultimate Explanation

This paper defends Explanatory Internalism, the view that while logical and mathematical principles apply universally, explanatory principles such as causation, sufficient reason, and modal necessity are domain relative and do not apply to existence considered as a totality. The position addresses cosmological and Principle of Sufficient Reason arguments by identifying a category error in extending internal explanatory norms beyond their conditions of application, rather than by denying explanation or intelligibility within the world. Explanatory relations require contrast classes, counterfactual structure, and parameter spaces of alternatives. These conditions obtain within domains of reality but fail at the level of totality. As a result, existence as such is neither necessary, contingent, nor brute in the standard metaphysical sense, since modal classification presupposes internal structure. The resulting view is structurally realist, non skeptical, and non quietist. It preserves the legitimacy of scientific and metaphysical explanation within the world while rejecting demands for ultimate explanation as ill posed rather than unanswered.