
A generic image of "moral power", the general rightfulness or wrongfulness of an idea to action, and the power of action produced therefrom.

A generic image of "moral power", the general rightfulness or wrongfulness of an idea to action, and the power of action produced therefrom.

In hmolscience, moral power refers to power, albeit not that of the "higher power" variety, but of the measurable scientific variety, related to human morals, specifically actions derived from moral choices or beliefs.

Goethe
In 1809, Goethe published Elective Affinities, wherein he outlined, in coded form, his theory of moral symbols of social interactions; a retrospect summary:

“The biographer Wolff is fairly typical in the language he uses to describe Goethe's relationship to Minna Herzlieb: ‘in her eye and being lay something naturally daemonic from which Goethe could not easily pull away’. Goethe, however, fought his passion with "sittlicher Kraft" [moral power], producing the fruit of Elective Affinities [Die Wahlverwandtschaften].”
— Astrida Tantillo (2001), Goethe’s Elective Affinities and the Critics (pg. 65)

In 1831, Goethe also discussed “moral power” with Johann Eckermann, who brought the term up, in respect to Kant’s categorical imperative. (Ѻ) In these translations, to note the German term "kraft" correctly translates as "force", hence "sittlicher Kraft" means "moral force", as opposed to Tantillo's translation above. The technical difference between force (or kraft), energy, and power, was not fully worked out until the late 19th century.

Material power | Moral power
In c.1875, Ralph Emerson, having already absorbed the "moral symbols" physico-chemical natural morality logic of Goethe (1809), began to dig thematically at the premise that "moral power" is but a higher level form of "material power", and that the former always lags behind the latter in development, understanding, and application; the main statement on this are as follows:

“Moral power has not kept pace with material power.”
— Ralph Emerson (c.1870) aggregate quote, in index of Volume 12 (Ѻ); in: Complete Works, Volume 7 (material power, pg. 166; moral power, 190), Volume 8 (moral power, pg. 316), Volume 10 (moral and material power, pgs. 64; material forces, 72)

“It is too plain that with the material power the moral progress has not kept pace. It appears that we have not made a judicious investment. Works and days [of Hesoid] were offered us, and we took works.”
— Ralph Emerson (c.1875), “Works and Days” (Ѻ); in: Complete Works, Volume 7 (pg. 166)

“We owe to books those general benefits which come from high intellectual action. Thus, I think, we often owe to them the perception of immortality. They impart sympathetic activity to the moral power.”
— Ralph Emerson (c.1875), “Books”; in: in: Complete Works, Volume 7 (pg. 190)

“Since everything in nature answers to a moral power, if any phenomenon remains brute and dark, it is that the corresponding faculty in the observer is not yet active.”
— Ralph Emerson (c.1875), Publication [8]

“Meantime we hate sniveling. I do not wish you to surpass others in any narrow or professional or monkish way. We like the natural greatness of health and wild power. I confess that I am as much taken by it in boys, and some-times in people not normal, nor educated, nor presentable, nor church-members, — even in persons open to the suspicion of irregular and immoral living, in Bohemians, — as in more orderly examples. For we must remember that in the lives of soldiers, sailors and men of large adventure, many of the stays and guards of our household life are wanting, and yet the opportunities and incentives to sublime daring and performance are often close at hand. We must have some charity for the sense of the people, which admires natural power, and will elect it over virtuous men who have less. It has this excuse, that natural is really allied to moral power, and may always be expected to approach it by its own instincts. Intellect at least is not stupid, and will see the force of morals over men, if it does not itself obey.”
— Ralph Emerson (c.1875), “Greatness”; in: Volume 8 (pg. 316)

“I believe in the closest affinity between moral and material power. Virtue and genius are always on the direct way to the control of the society in which they are found. It is the interest of society that good men should govern, and there is always a tendency so to place them.”
— Ralph Emerson (c.1875), “Aristocracy”; in: Volume 10 (pgs. 64)

“These forces are in an ascending series, but seem to leave no room for the individual; man or atom, he only shares them; he sails the way these irresistible winds blow. Intellect and morals appear only the material forces on a higher plane. The laws of material nature run up into the invisible world of the mind, and hereby we acquire a key to those sublimities which skulk and hide in the caverns of human consciousness. And in the impenetrable mystery which hides—and hides through absolute transparency— the mental nature, I await the insight which our advancing knowledge of material laws shall furnish!”
— Ralph Emerson (1877), “Perpetual Forces” (pdf), The North American Review, Volume 125, Sep 1; in: Completed Works, Volume 10 (pg. 72) [1]

Emerson, of note, in these promulgations, used the term "spiritual', here and there; his citation of scientists, e.g. Faraday, and straight science, e.g. “I delight in tracing these wonderful ‘powers’, the electricity and gravity of the human world” (Perpetual Forces, 1877), however, seem to well enough obviate the former obsolete terminology usages (see: spirit terminology reform), retrospectively speaking.

Quotes
The following are related quotes:

“Even in war, moral power is to physical power as three parts out of four.”
— Napoleon Bonaparte (c.1817), Publication (Ѻ)

See also
● Moral chemistry
● Moral philosophy
● Moral science

References
1. Emerson, Ralph. (1877). “Perpetual Forces” (txt)(pdf), The North American Review, Volume 125, Sep 1; in: Completed Works, Volume 10 (pg. 72)