Simplicity occupies a contested and multi-valent position across the depth-psychology corpus. Far from designating mere plainness or reduction, it functions as a philosophical ideal whose meaning shifts dramatically depending on the tradition invoking it. In Platonic and Neoplatonic streams, simplicity names the irreducible unity that underlies manifest multiplicity — Ibn Sina’s metaphysical quest for beings that are ‘irreducibly themselves,’ Plotinus’s account of the One whose absolute simplicity generates Mind and Soul, and Plato’s identification of beauty, harmony, and virtue with ‘the true simplicity of a rightly and nobly ordered mind.’ Here simplicity is ontologically primary and epistemically supreme. In contrast, McGilchrist reverses the valuation: simplicity is not the ground of reality but a special, diminished case of complexity — a feature of our models, not of the reality modelled. The Taoist current, represented through the I Ching commentaries, locates simplicity in the ‘natural endowment of heaven and earth,’ an innate capacity lost when the human mentality becomes conditioned and artificial. Marcus Aurelius treats it as a moral quality whose authentic form needs no proclamation, while Hillman warns that the seduction of simplicity pacifies the mind and saps power. John Climacus names it ‘the first characteristic of childhood,’ recoverable through hard spiritual labour. Taken together, these positions reveal a fundamental tension: simplicity as originary ground versus simplicity as epistemic reduction, and simplicity as virtue versus simplicity as naïveté.