What I Mean by 'Metaphysics'

After publishing “A Minimum Viable Metaphysics,” readers asked the right question: what exactly is metaphysics? Not “mystical speculation” or “armchair philosophy”—but what? The clearest answer comes from distinguishing it from two other rigorous modes of inquiry: mathematics and science.

Mathematics and logic trade in proof. They begin with axioms and definitions, then deduce consequences through formal rules. A conjecture becomes a theorem only when the deductive chain is complete. The standard is certainty within a formal system. Crucially, mathematics and logic don’t need the physical universe to exist at all—they operate in the realm of pure form and relation.

Science, by contrast, trades in testable understanding of the physical world. Scientists begin abductively, forming hypotheses to explain puzzling observations. They then deduce what those hypotheses predict and test those predictions against reality. When evidence comes in, they update their confidence inductively—through statistics, Bayesian reasoning, or accumulated observation. The cycle repeats: guess, deduce consequences, test, update, guess better. The standard is empirical adequacy.

Metaphysics, as I use the term, articulates the background commitments that make scientific inquiry into the physical world possible. These commitments can’t be proven like mathematical theorems—they’re about the world, not about formal systems. They can’t be tested like scientific hypotheses—you need them already in place to do any testing. Yet without them, empirical investigation can’t get started.

Consider the three commitments from my essay: that reality exists independently of our minds (the Reality Principle), that the universe began with asymmetries (the Asymmetry Principle), and that there’s a lawful layer to nature (the Lawfulness Principle). Mathematics can’t prove physical reality exists—it works the same whether or not there’s a world to count. You can’t test them scientifically without already assuming them. Yet deny any of them and watch empirical inquiry collapse: no stable world to measure, no reason patterns would emerge, no ground for expecting tomorrow to resemble today.

Take causation as a concrete example. When a scientist designs an experiment, she assumes that manipulating variable X will reliably affect outcome Y—that causes precede effects, that similar initial conditions yield similar results. She doesn’t test this assumption in her experiment; she needs it to design the experiment in the first place. That’s the Lawfulness Principle doing its work: not as a hypothesis under investigation, but as part of the scaffold that makes hypothesis-testing possible.

So how does metaphysics proceed? Primarily through abduction—inference to the best explanation. We ask: which minimal set of commitments best accounts for the success of science and the intelligibility of everyday experience?

Deduction then ensures these commitments cohere with each other—that they don’t contradict or smuggle in hidden assumptions.

Finally, induction keeps them honest by checking them against what our best sciences have discovered. If your metaphysics conflicts with robust scientific findings, something has gone wrong.

Before going further, two clarifications to prevent confusion. When I say “induction,” I mean learning from evidence, not mathematical induction, which is actually a deductive technique. And when I say these commitments are about lawfulness, I don’t mean our current physics is final—just that some stratum of regularity exists for science to discover.

Think of it this way: Mathematics and logic ask “what follows from these axioms?” Science asks “what does the evidence support?” Metaphysics asks “what must we assume about reality for evidence to matter?”

This is why I call my approach “minimum viable”—borrowing from the tech world’s notion of doing just enough to get the job done. We need some metaphysical commitments or empirical inquiry can’t begin. But we want as few as possible, stated as clearly as possible, held as lightly as possible. Not a palace of certainties but a scaffold for investigation.

This is not a novel observation—philosophers from Kant to Quine have noted that inquiry requires starting points. The novelty, if any, is the emphasis on minimality: carrying only what’s necessary, stated as explicitly as possible.

The upshot: metaphysics means explicitly stating the assumptions about physical reality that make empirical inquiry possible. It identifies the planks we must stand on when neither proof nor decisive experiment is available.

Keep those planks minimal, explicit, and revisable. That’s scaffolding that enables work, not a monument that merely impresses.

The goal isn’t philosophical grandeur but philosophical honesty: admitting what we must assume, and assuming nothing more.

To see these commitments at work—from cosmology to consciousness, from quarks to culture—read the main essay at jimrutt.substack.com.