POWER: The ability to do something or act in a particular way, especially as a faculty or quality
POTENCY: The power of something to affect the mind or body
These primary definitions show a tendency to speak of "power" in terms of physical action, whereas "potency" can affect "mind or body."
This in turn lines up with my distinctions between the marvelous and the uncanny. I've consistently defined the marvelous as some object, entity or occurrence that breaks with causal law, be it something nominally justified through some new scientific technique-- Verne's Nautilus, obviously-- or something with no justification at all, like a cartoon rabbit who can defy gravity when it happens to be funny to do so. Not all marvelous entities register as having high dynamicity, as I pointed out here, yet even a character whose marvelous nature gives him no special power of physical action still displays a "power" to flout natural law.
Going by the Oxford definition, though, "potency" can be used to affect both the physical and the mental planes of existence, or, as Octavio Paz put it, "body" and "non-body." Paz's dichotomy was useful to me in sorting out the three phenomenalities with respect to a bifurcated causality in THE INTELLIGIBILITY QUOTIENT PT. 2:
...both the "naturalistic" and "marvelous" phenomenalities are unitary in terms of what I chose at that time to call the aspects of "body" and "non-body"-- also roughly comparable to Cassirer's "causality" and "efficacy." In contrast, the phenomenenality of "the uncanny" was one in which "body" was at odds with "non-body."
G. Wilson Knight's essay on HAMLET implies this opposition between body and non-body when, as I showed in Part 1, Knight imputed to the moody Prince of Denmark a power that was not a literal power, saying that "the poison of [Hamlet's] mental essence spreads outward among things of flesh and blood, like acid eating into metal." When he wrote this, Knight was not being at all literal, as his use of the acid simile demonstrates. Hamlet has no more physical power than any other human being, but because he has "held converse with death," he *SEEMS LIKE* he has become something more than human. But the "seeming" takes place purely upon the mental/spiritual/"non-body" plane of being.
Until reading Knight, I had always classified HAMLET and most of its film adaptations as instances of the trope I call "phantasmal figuration." However, Knight's description makes Hamlet sound very much like the type of uncanny-or-naturalistic figure of another trope: "the perilous psycho." In terms of the play proper, one may argue back and forth whether or not Hamlet, in feigning madness, may have actually gone mad. But whether the Danish prince is mad or merely infected with a pestilential cynicism, his attitude has given him a special "potency," even though he has no special power-- just like all of the "psycho" characters I've studied.
The primary subject of the aforementioned INTELLIGIBITY essay was to survey instances of my ten phenomenality tropes, in both their naturalistic and uncanny manifestations. I demonstrated that even though all of the cited examples fell within the bounds of causal coherence, the "uncanny" examples broke with causal intelligibility while the "naturalistic" ones did not. Now I refine that statement to add that the process of breaking with causal intelligibility is one that also confers a "potency" that is not "power."
The above phrase *SEEMS LIKE* proves applicable to all of the chosen examples, and, I assume, to any other examples that might be provided:
The Moby Dick of Melville's novel is identical in POWER to the Moby Dick of John Huson's 1956 film-adaptation. However, the original White Whale surpasses his naturalistic imitation in POTENCY, precisely because he *SEEMS LIKE* he is more than an ordinary whale.
Tod Slaughter's naturalistic perpetrator of "bizarre crimes" Perceval Glyde has no more POWER than the actor's more famous character Sweeney Todd, but Sweeney exceeds Glyde in POTENCY because he *SEEMS LIKE* more than a common criminal.
Hawk of the Wilderness and Tarzan are equals in POWER-- indeed, Olympic star Bruce Bennett played both-- but Tarzan clearly *SEEMS LIKE* he is more than a mortal man, even though he is not-- and the same applies to the huge horde of animal-skinned jungle-people who have imitated Tarzan.
And finally-- since I need not repeat the formula for all ten-- "perilous psycho" Joanna Eris of EYE OF THE BEHOLDER kills men for the crimes of her father, just as the fellow who popularized the very term "psycho" kills women for the crimes of his mother. But even though Norman Bates isn't a particularly powerful example of a psycho-- as I mentioned here-- he *SEEMS LIKE* he has a far greater ability to dispense death.
In contrast to the Oxford definition above, then, I will use "potency" exclusively to denote this semblance of a "non-body" form of *dynamicity.* However, since in earlier essays I've defined "dynamicity* exclusively in terms of that power that affect physical bodies within a given narrative, at best potency must be interpreted as extrinsic, rather than intrinsic. to that narrative-- which may line it up more properly with my conception of the combinatory-sublime.