Hierarchy

Hierarchy, in Objectivism, is the structure of human knowledge: every concept and every conclusion rests on ones that had to be reached first, and the whole structure rests on perception. It follows that an item of knowledge cannot be validated in isolation, only by tracing the order in which it was earned.

“New concepts can be formed by integrating earlier-formed concepts into wider categories, or by subdividing them into narrower categories... But all concepts are ultimately reducible to their base in perceptual entities, which are the base (the given) of man's cognitive development.”
   ~ Ayn Rand, "Concept-Formation", Introduction to Objectivist Epistemology

Order in knowledge

Some things cannot be learned before others. A child forms "table" before "furniture", and "furniture" before "artifact", because the wider concept is an integration of narrower ones already held. He forms concepts of entities before concepts of attributes, because an attribute is an attribute of something.

The chain runs in one direction and terminates:

perceptual entities → first-level concepts (table, chair) → wider abstractions (furniture) → still wider (artifact)

First-level concepts are those formed directly from perceptual observation. Everything above them is an abstraction from abstractions, and everything is ultimately reducible to the perceptual level, which is the given. See Concept formation and Perception.

Hierarchy is best understood as an aspect of context: the lower-level knowledge a conclusion depends on is part of the context conditioning it, whether or not anyone has it in mind at the time.

Reduction

The practical use of the idea is reduction: taking an abstract conclusion and retracing the steps back down to the observations that support it.

This is how Objectivism proposes to test whether a person actually holds an idea or merely holds a word. Someone who cannot get from "justice" to the concretes it was formed from has a floating abstraction — a term with the connection to reality missing. The error is characteristic of rationalism, which builds elaborate structures on premises never traced down.

Reduction is also what proof consists of. To prove a proposition is to establish its relationship, through the hierarchy, to the evidence of the senses. See Proof and Logic.

Hierarchy and fallacies

Two of the errors Objectivism names are hierarchy violations:

• The stolen concept: using a concept while denying one it depends on. An argument that reason is invalid must be reasoned; a claim that nothing can be known claims knowledge.
• Context-dropping: applying a conclusion outside the conditions it was established under, which usually means having lost track of what those conditions were.

Both are invisible unless the order of dependence is kept in view, which is why Objectivism treats hierarchy as a working tool rather than a description.

Common misunderstandings

• That hierarchy means some concepts are more important than others. It concerns order of dependence, not value. "Table" is more fundamental than "furniture" in the sense that it must come first, not in the sense that it matters more.
• That the order is the same for everyone in every detail. The broad structure is set by the facts — attributes presuppose entities for anyone — but which particular first-level concepts a given person formed first depends on what he encountered.
• That reduction means every idea must be re-derived before use. The point is that the derivation is available if challenged. A conclusion once validated is held, not rebuilt.
• That the word carries its ordinary sense of a chain of command. The Greek root is the same, but here it names a structure of dependence among ideas, with no authority involved.

See also

• Context · Knowledge · Proof · Definitions · Fundamental · Rule of Fundamentality
• Concept · Concept formation · Conceptual Common Denominator · Unit-economy
• Perception · Senses · Reason · Logic · Induction
• Floating Abstraction · Fallacy of the stolen concept · Rationalism

Discussion

• Aristotle's wheel paradox
• A criticism of Objectivist epistemology
• Objectivist epistemology and metaphysics

References

• Rand, Ayn. "Abstraction from Abstractions" and "Definitions", Introduction to Objectivist Epistemology. The Objectivist, 1967.
• Peikoff, Leonard. Objectivism: The Philosophy of Ayn Rand, chapter 4.