Do not fear that I shall speak to you of inherited ideas. Far from it. The autonomous contents of the unconscious, or, as I have called them, dominants, are not inherited ideas but inherited possibilities, not to say compelling necessities, for reproducing the images and ideas by which these dominants have always been expressed. Of course every region of the earth and every epoch has its own distinctive language, and this can be endlessly varied. It matters little if the mythological hero conquers now a dragon, now a fish or some other monster; the fundamental motif remains the same, and that is the common property of mankind, not the ephemeral formulations of different regions and epochs.
— Carl Gustav Jung
The distinction Jung is drawing here is finer than it first appears, and it carries more weight than most readers give it. What is inherited is not a thought but a pressure — a necessity, as Jung says, for reproducing certain kinds of images under certain kinds of conditions. The archetypal layer of the psyche is not a library of pictures stored somewhere in the neurons; it is more like a magnetic field that orients iron filings into pattern without itself being visible. The filings are the images a particular culture, a particular language, a particular moment in history provides. The field is something else entirely.
This matters because the objection to Jung's theory of archetypes almost always attacks the wrong target — it imagines that Jung is claiming Amazonian hunter-gatherers and medieval monks share the same mental furniture, the same dragon-image. They do not. What they share is the probability of dragon-logic: that the encounter with something overwhelming and annihilating will configure itself into a figure with teeth. The monster changes. The necessity of the monster, in that particular existential pressure, does not. Mythology's surface variety is not evidence against the archetypes — it is exactly what the theory predicts.
Carl Gustav Jung·The Structure and Dynamics of the Psyche·1960