Debunking arguments typically attempt to show that a set of beliefs or other intensional mental states bear no appropriate explanatory connection to the facts they purport to be about. That is, a debunking argument will attempt to show that beliefs about p are not held because of the facts about p. Such beliefs, if true, would then only be accidentally so. Thus, their causal origins constitute an undermining defeater. Debunking arguments arise in various philosophical domains, targeting beliefs about morality, the existence of God, logic, and others. They have also arisen in material-object metaphysics, often aimed at debunking common-sense ontology. And while most of these arguments feature appeals to ‘biological and cultural contingencies’ that are ostensibly responsible for our beliefs about which kinds of objects exist, few of them take a serious look at what those contingencies might actually be. The purpose of this paper is twofold. First, to remedy this by providing empirical substantiation for a key premise in these debunking arguments by examining data from cognitive science, evolutionary biology, and developmental psychology that support a ‘debunking explanation’ of our common-sense beliefs and intuitions about which objects exist. Second, to argue that such data also undermines a particular kind of rationalist defense of common-sense ontology, sometimes employed as a response to the debunking threat.