Abstract

This paper develops a proposition-first, property-based account of causality and explanation, and introduces an epistemic meta-metaphysical principle, Explainability, as a refinement of Leibniz’s Principle of Sufficient Reason. It argues that much traditional metaphysics of causation, existence, and cosmological explanation is distorted by the grammar of natural language and by naive uses of part–whole structure. Subject–predicate form and ordinary “why”-questions encourage three systematic errors: treating causation as a primitive relation between entities rather than structured dependence among properties and state-transitions; reifying totalities such as “the universe” or “the series of contingent beings” as additional entities in the domain; and treating existence as a first-order property capable of causal explanation. Against this background, the paper reinterprets Aristotle’s causal schema as explanatory grammar rather than deep ontology, and examines Descartes, Hume, and Kant as cases in which causal doctrines become self-referentially unstable when their own claims are treated as propositions subject to their stated epistemic constraints. The paper then reconstructs PSR in propositional form and shows how its cosmological application relies on an illicit mereological move from parts to wholes. The Principle of Explainability is proposed as an epistemic constraint on metaphysical theorizing: every true proposition must admit of an explanation that yields indispensable knowledge of why it is true, articulated in terms of properties, states, and event-relations rather than entity-level causal primitives. On this view, metaphysics is reoriented away from the search for a cause of “being as such” and toward mapping the explanatory structure of truths under disciplined logical and mereological constraints.