Within the depth-psychology corpus, ‘Association’ occupies a uniquely foundational position: it is simultaneously Jung’s primary empirical instrument, a theoretical window onto the unconscious, and the diagnostic gateway to the complex. The term enters the literature first as a laboratory procedure — the Word Association Experiment developed with Riklin at the Burghölzli — where reaction-times, disturbances, and perseverations become measurable indices of affectively charged unconscious contents. Yet Jung is careful to insist that no association is a mere mechanical linkage: every response is the resultant of the subject’s entire psychological past, and a carefully devised stimulus-word functions as a surrogate for real-life situations, evoking feeling-toned complexes that consciousness has suppressed or never fully registered. The classificatory schemas of Aschaffenburg, Ziehen, Mayer, and Claparède are surveyed and found useful but always partial; none can exhaust the individual possibilities. Beyond the experiment itself, ‘association’ ramifies into adjacent territory — psychoanalysis, dream-interpretation, hysteria, dementia praecox, family constellation, and the galvanometric measurement of psychophysical reactions. Free association, explicitly contrasted with the structured word-association method, appears as the Freudian variant; Jung’s method retains the structure precisely to render the complex’s interference legible. The broader theoretical implication is that consciousness plays ‘only a minor role in the process of association’: the real determinants are unconscious feeling-toned constellations, making the association experiment a privileged portal to the depths.