Builes’s Modal Idealism

Philosopher David Builes argues for a thesis that goes even beyond Idealism, which is the view that “every fundamental entity is conscious, and moreover every fundamental property is a phenomenal property (i.e., a property that specifies what it’s like to be something).” Builes makes the claim that “it is metaphysically necessary that Idealism is true,” a startlingly radical position he calls Modal Idealism (Builes, 2024).

Building his metaphysical argument on a far-reaching reinterpretation of the ontology of possible worlds, Builes asserts that only one possible world exists in a fundamental sense, and all other possible worlds exist as ideas in the mind of a divine being (or a structurally similar ideal observer). This theory combines a respect for elements of idealism (the view that reality is fundamentally mental) and for modal realism (the view that other possible worlds are as real as the actual world), but reconceives possible worlds as divine thoughts, not concrete entities. He writes, “All possible worlds exist, but only one world is fundamental. The other possible worlds exist as thoughts in the mind of a divine being” (Builes, 2024).

Possible Worlds as Divine Thoughts

Builes gives four different arguments for Modal Idealism. He writes, “First, I argue that, if at least some possible fundamental properties are phenomenal properties, then the denial of Modal Idealism leads to implausible brute necessities. Second, I argue that those who endorse the Eleatic Principle, according to which it is necessary that all concrete objects have causal powers, should endorse Modal Idealism. Third, I argue that Modal Idealism helps us secure our knowledge of our own conscious states in the face of influential “debunking” arguments. Fourth, I argue that Modal Idealism is theoretically fruitful: it allows us to make substantial progress on several perennial metaphysical debates beyond the philosophy of mind” (Builes, 2024).

Arguments and Implications

The claim is that Builes’s Modal Idealism maintains ontological parsimony: only one world is metaphysically fundamental, while all possible worlds are intentional objects in the mind of a divine intellect, whose mind is rich enough to contain precise, structured representations of all possible worlds. He says, “All the other possible worlds exist, but they do so in virtue of being represented by a mental being.”

Builes argues that Modal Idealism “…offers an elegant unification of modal metaphysics and philosophy of mind.” It reframes modal truths as mental representations, allowing for a streamlined and potentially theistic-compatible ontology that treats modality as a matter of divine will or cognition.

A corollary is the need for grounding. The actual world’s existence is ungrounded; it is fundamental—whereas the existence of non-actual possible worlds is grounded in the mental activity of this ideal observer, the divine presence.