“I really agree that Yog-Sothoth is a basically immature conception, & unfitted for really serious literature. The fact is, I have never approached serious literature yet. But I consider the use of actual folk-myths as even more childish than the use of new artificial myths, since in the former one is forced to retain many blatant peurilities & contradictions of experienced which could be subtilised or smoothed over if the supernaturalism were modelled to order for the given case. The only permanently artistic use of Yog-Sothothery, I think, is in symbolic or associative phantasy of the frankly poetic type; in which fixed dream-patterns of the natural organism are given an embodiment & crystallisation... But there is another phase of cosmic phantasy (which may or may not include frank Yog-Sothothery) whose foundations appear to me as better grounded than those of ordinary oneiroscopy; personal limitations regarding the sense of outsideness. I refer to the aesthetic crystallisation of that burning & inextinguishable feeling of mixed wonder & oppression which the sensitive imagination experiences upon scaling itself & its restrictions against the vast & provocative abyss of the unknown. This has always been the chief emotion in my psychology; & whilst it obviously figures less in the psychology of the majority, it is clearly a well-defined & permanent factor from which very few sensitive persons are wholly free.... Reason as we may, we cannot destroy a normal perception of the highly limited & fragmentary nature of our visible world of perception & experience as scaled against the outside abyss of unthinkable galaxies & unplumbed dimensions—an abyss wherein our solar system is the merest dot... The time has come when the normal revolt against time, space, & matter must assume a form not overtly incompatible with what is known of reality—when it must be gratified by images forming supplements rather than contradictions of the visible & measurable universe. And what, if not a form of non-supernatural cosmic art, is to pacify this sense of revolt—as well as gratify the cognate sense of curiosity?”

Letter to Frank Belknap Long (27 February 1931), in Selected Letters III, 1929-1931 edited by August Derleth and Donald Wandrei, p. 293
Non-Fiction, Letters, to Frank Belknap Long
Context: I really agree that Yog-Sothoth is a basically immature conception, & unfitted for really serious literature. The fact is, I have never approached serious literature yet. But I consider the use of actual folk-myths as even more childish than the use of new artificial myths, since in the former one is forced to retain many blatant peurilities & contradictions of experienced which could be subtilised or smoothed over if the supernaturalism were modelled to order for the given case. The only permanently artistic use of Yog-Sothothery, I think, is in symbolic or associative phantasy of the frankly poetic type; in which fixed dream-patterns of the natural organism are given an embodiment & crystallisation... But there is another phase of cosmic phantasy (which may or may not include frank Yog-Sothothery) whose foundations appear to me as better grounded than those of ordinary oneiroscopy; personal limitations regarding the sense of outsideness. I refer to the aesthetic crystallisation of that burning & inextinguishable feeling of mixed wonder & oppression which the sensitive imagination experiences upon scaling itself & its restrictions against the vast & provocative abyss of the unknown. This has always been the chief emotion in my psychology; & whilst it obviously figures less in the psychology of the majority, it is clearly a well-defined & permanent factor from which very few sensitive persons are wholly free.... Reason as we may, we cannot destroy a normal perception of the highly limited & fragmentary nature of our visible world of perception & experience as scaled against the outside abyss of unthinkable galaxies & unplumbed dimensions—an abyss wherein our solar system is the merest dot... The time has come when the normal revolt against time, space, & matter must assume a form not overtly incompatible with what is known of reality—when it must be gratified by images forming supplements rather than contradictions of the visible & measurable universe. And what, if not a form of non-supernatural cosmic art, is to pacify this sense of revolt—as well as gratify the cognate sense of curiosity?