Phillip Ngo
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Concept

Auxiliary Function

The second-most-differentiated function in a Jungian type — necessarily of *different kind* from the principal (judging if the principal perceives, perceiving if the principal judges) — that supplies what the principal cannot supply alone, and serves as the bridge toward the more deeply unconscious inferior-function.

3 min

Working Definition

carl-jung in psychological-types is precise: "Naturally only those functions can appear as auxiliary whose nature is not opposed to the leading function. For instance, feeling can never act as the second function by the side of thinking, because its nature stands in too strong a contrast to thinking." Two judging functions cannot cohabit at top of consciousness because they would cancel each other. Hence:

  • Thinking principal → auxiliary is sensation or intuition (perceiving).
  • Feeling principal → auxiliary is sensation or intuition.
  • Sensation principal → auxiliary is thinking or feeling (judging).
  • Intuition principal → auxiliary is thinking or feeling.

In MBTI's elaboration, the auxiliary further takes the opposite attitude from the principal — a dominant introverted intuitive (Ni) has an extraverted auxiliary (Te or Fe), bringing the introvert into the world. This balancing is what Myers identified as crucial and surfaces via the J/P axis.

How Different Authors Frame It

  • carl-jung in psychological-types: A second function of different kind, complementary to the principal. Of inferior differentiation but still conscious and usable.

(Future: Myers operationalizes the auxiliary's attitude — the principal's introversion is balanced by the auxiliary's extraversion (or vice versa). Beebe's eight-function model gives the auxiliary the archetypal role of "the parent.")

Mechanism / How It Works

The auxiliary makes the principal workable. A principal function with no developed auxiliary is one-sided and brittle. The thinking type with no perceiving auxiliary has nothing to think about; the intuitive with no judging auxiliary cannot decide among the possibilities perceived.

Developmentally, Jungian writers (and MBTI theorists like Mary McCaulley) propose a typical lifespan pattern: childhood and early adulthood develop the principal; the auxiliary comes online robustly in the 20s–30s; the tertiary in the 40s; the inferior approaches consciousness from the 40s onward. This is heuristic, not strict.

The auxiliary is the bridge to the inferior. The inferior cannot be reached directly (too primitive); the auxiliary, which shares one half of its nature with the principal and is reachable from consciousness, is the route by which the inferior is gradually approached.

Practical Use

  • Career. Mid-career role design should engage both principal and auxiliary. A thinker who has not developed sensation or intuition auxiliary is intellectually stuck — competent in the abstract but unable to gather the right data.
  • Development. Before working on the inferior, develop the auxiliary. The most efficient adult-development move is to identify and exercise the second function deliberately for a year before approaching the inferior.
  • Parenting / teaching. Children whose auxiliary is suppressed (by a parent who only rewards the principal) develop a fragile one-sided personality. The auxiliary should be cultivated, not the principal alone.

Tensions ⚠

  • Auxiliary's attitude. Jung is somewhat ambiguous about whether the auxiliary necessarily takes the opposite attitude from the principal. Myers insisted on it; some classical Jungians read Jung as allowing same-attitude auxiliary. This is the technical seam where Myers extends Jung.
  • Tertiary vs. auxiliary debate. Whether the tertiary is the same attitude as the principal (Beebe) or the same attitude as the auxiliary (some MBTI writers) is contested.

Frameworks That Use This Concept

  • jungian-types — central architectural element.
  • mbti — operationalized via the J/P axis.

Sources Discussing This Concept