Philosophy
The correct chain, and where a popular account of it adds a branch that doesn’t belong.
The Chain
Metaphysics (what is real) and Epistemology (how you know it) together give rise to Ethics (how you should act, given both). Epistemology itself already presupposes Metaphysics — you need something real before you can have a theory of knowing it — but Ethics draws on both directly, not just on Epistemology at one remove: it needs Epistemology’s “reason is man’s means of knowledge” and Metaphysics’s “man has this specific, volitional nature” as two separate inputs, not one filtered through the other.
Objectivism gets this part right, and so does this vault. Where it goes wrong is the next step. Peikoff’s Introduction to Objectivism (and OPAR) present five branches — Metaphysics, Epistemology, Ethics, Politics, Aesthetics — treating Politics as a fourth, co-equal branch that specifies which social/institutional system a correct ethics implies, and concluding that this implies a government: a coercive territorial monopoly on the use of retaliatory force. Rand’s “The Nature of Government” argues explicitly against anarchism on the grounds that competing enforcement agencies can’t produce objective law.
There is no fourth branch. Politics dissolves into two things, and neither of them is a branch.
1. Law — Already Inside Ethics
Law is what remains once the illegitimate institutional claim is stripped out of “Politics”: the subset of ethics that deals with resolving Conflicts — which uses of force are legitimate (retaliatory) and which aren’t (initiatory). This is where The Non-aggression Principle lives. It presupposes no particular enforcement institution — it’s a purely normative claim about what’s permitted, derived the same way the rest of ethics is: from man’s nature as a rational, volitional being.
Rand actually gets this derivation right — rights, for her, are moral principles, not legal grants. The error is the next, separate move.
2. The Institutional Question — Not Philosophy, Economics
“Given the Law above, what arrangement of institutions actually secures it without becoming a violator of it itself?” is not an ethical question — it’s empirical and economic. Objectivism answers it by fiat: “objective law requires one final, non-competing arbiter,” treating a monopoly on force as definitionally required for objectivity. That’s a category error. Objectivity is a property of the standard — does it derive from reason applied to reality — not of there being exactly one institution that applies it. Nobody thinks science stops being objective for lack of a single monopoly Scientist; competing, independent adjudicators bound by the same standard is exactly how objectivity survives contact with fallible individual judgment, in law as in science.
Once it’s seen as an institutional question, it’s economics‘s job to answer, not philosophy’s — specifically the economic calculation problem and the knowledge problem: a monopoly can’t be disciplined by exit, and a monopoly on force is the one monopoly that can’t be checked by anything else, because it’s the thing that would have to permit being checked. See State and The Myth of Limited Government.
Where Economics Fits — Parallel, Not Stacked
Economics (praxeology) isn’t a branch of philosophy at all. It doesn’t sit inside the Metaphysics → Epistemology → Ethics chain — it’s a separate, positive (value-free) formal science, built on its own axiom (Axiom of Action), describing what happens when scarce means are used to pursue chosen ends, regardless of whether those means were acquired justly. It doesn’t need Ethics to reach its conclusions.
What’s striking is that it doesn’t need to. Run the economics forward and coercion — Parasitism, violated property, broken price signals — collapses into calculation chaos on its own terms, with no “ought” invoked anywhere. Socialism is impossible is a praxeological conclusion, not a moral one. That it lands on the same prohibition Ethics reaches by a completely independent route (performative self-contradiction, not consequences) isn’t the two branches being “the same.” It’s two unrelated proofs hitting the same wall — which is stronger evidence the wall is real than either proof alone.
Worth being precise about which layer of economics this independence applies to, though. Bare praxeology — purposeful action given scarce means — needs no prior concept of property; even a thief is “acting” in the technical sense. But market economics specifically — trade, prices, the division of labor, everything built on the coincidence of wants — presupposes title. Exchange only means something between two parties who each already own what they’re trading. That concept of “mine” versus “thine” is Law’s contribution, not economics’. So market economics, unlike bare praxeology, does build directly on top of Law: one premise (what may rightfully be traded) supplied by Ethics, the rest (what happens once trading occurs) worked out independently by economics.
Diagram
Aesthetics
Objectivism’s fifth branch — now written up in full at Aesthetics. Short version: art is what lets a conceptual mind actually see its own philosophy, concretized into something perceptible; Rand’s own schema derives it from Ethics, not straight from Metaphysics, the same way this vault derives Law from Ethics. Unlike Politics, nothing about it smuggles in an institution — there’s nothing here for the anarchist correction above to touch.