Freud, Fraud, Resistance and Denial
And the most towering figure in modern times in that "knowledge gap" must be considered to be Freud's:
Leaving aside his early "work" with animal magnetism, electrotherapy, and the "nasal reflex" (tweakable by cocaine), let us turn to his "mature" and what he himself considered his seminal work, The Interpretation of Dreams, in which he maintains that dreams represent wish-fulfillment, and, to meet objections involving cases like, say, The Shark Dream, came up with the splendid weaseling that in such cases you must look not at the "manifest" but the "latent" content of such dreams—that is, whatever interpretation the interpreter wishes to levy on them that makes them wish-fulfillment.
But Freud was only getting started there, because, after the splendid invention of the distinction between the "manifest" and "latent" content of dreams, he came up with what must be regarded as the central fraud of all the modern "psychist" pseudosciences, the perfectly splendid concept of the "unconscious" or "subconscious" mind (think about it, if you're capable and willing), which allows the "analyst" to impute any motives or desires he or she desires to the "analyzee" (see, famously, Freud's own further invention, the "Oedipus complex", in which he imputes parricidal and incestuous longings to everyone).
And if the "analyzee" disagreed or disagrees, why, that was and is "resistance" to a good Freudian psychoanalyst, which he or she takes to be just "another" "symptom" of the analyzee's "mental illness".
"Resistance", however, seems to've been a little too frank for the modern practitioners and polity of the psychosociocratic doctor state, and so "resistance" has been re-dubbed "denial".
And, indeed, have you noticed how the world today is filled with snap and long-distance "diagnoses" of "mental illnesses" ("phobias" and—for some reason—"addictions"/"dependences" rather than "philias") of various kinds, accompanied by a perfect storm of auxiliary "diagnoses" and cries of "denial"?
Keywords: addictions, dependences, denial, doctor state, Freud, fraud, "mental illness", phobias, pseudomedicine, pseudoscience, psychiatry, psychism, psychoanalysis, psychology, psychosociocracy, resistance, socism, spirism, Szasz, totalitarianism, totalitarian studies