What kind of language is that? What does it mean, and should we care? It's poetic language, and it refers to things we don't comprehend easily via other ways of speaking. The author of Ephesians referred to struggling, "not against men, but against Principalities and Powers." [6:12] Christians for nearly 2000 years since then have found those words enlightening, including Walter Wink, a contemporary theologian and lifelong activist.
According to Wink: "We moderns cannot bring ourselves by any feat of will or imagination to believe in the real existence of these mythological entities that traditionally have been lumped under the general category "principalities and powers." But this statement begins a series of books for moderns, exploring that very concept. Because it fits too well with phenomena we encounter--not (he admits) as "invisible demonic beings flapping around in the sky, occasionally targeting some luckless mortal with their malignant payload of disease, lust, possession, or death"-- but in the entrenched background assumptions of people who rule and speak for us, the intractable perversities of institutional policy, the invisible blind spots in even our own well-considered opinions.[Naming the Powers pg 5 Fortress Press, 1984]
His predecessor William Stringfellow, a Harlem attorney active in the movements for civil rights and against the US/Vietnam war, also found use for this terminology. "There is nothing particularly mysterious, superstitious, or imaginary about principalities... The realities to which the biblical terms 'principalities and powers' refer are quite familiar to modern society, though they may be called by different names. What the Bible calls 'principalities and powers" are called in contemporary language 'ideologies,' 'institutions,' and 'images.'
"A principality, whatever its particular form and variety, is a living reality, distinguishable from human and other organic life. It is not made or instituted by men, but, as with men and all creation, made by God for his own pleasure." [Free in Obedience, Seabury Press 1964 pg 52]
Stringfellow gave examples. Marilyn Monroe, when he wrote, was a potent 'image.' Although she herself had recently died, "there were two lives that claimed and used that name, one a principality, the other a person... In fact, every person is accompanied in his life by an image; he is often controlled or destroyed by his image, and often it survives him." [pg 53]
Hitler was a less benign example: "It may well be that long before his actual suicide the person named Hitler had been altogether obliterated by the principality called Hitler; that the person had indeed been possessed by a demon of that name, and that the devastation and massacre wrought in the name of Hitler was not the work of just some dark genius of the man, nor even of the man's insanity or gross criminality, but of the awesome demonic power that possessed him." [pg 55]
Few of us have images of such power, but everyone's image enjoys a little worship, and so we must struggle against demands that we "give up [our] life as a person to the service and homage of the image."  Not only are Quakers not immune; Quaker traditions of dedication and service may well make us particularly susceptible!
"Institutions" need little explanation; we know many examples, some few of which may even be benign. But "in the end, the claim for service which an institution makes upon a man is an invitation to surrender his life in order that the institution be preserved and prosper. It is an invitation to bondage."  Of course this is perfectly customary and taken for granted, but it deserves more thought than it gets.
"Ideologies" include the obvious pejorative examples--Communism, fascism, racism and the like but also: "Humanism, capitalism, democracy, rationalism--though Americans think of these as benevolent powers." 
Stringfellow's categories naturally overlap, and can't cover all possible examples; "Sex, fashion, and sports are all among the angelic powers." So, particularly, is "money." 
"Like all men and all things, the angelic powers and principalities are fallen and become demonic powers. 'Demonic' does not mean evil; the word refers rather to death, to fallenness." 
Fallen? There's another unsettling word. Modern-day Quakers don't often call anything "fallen," or "demonic." Most modern Quakers probably don't believe in "The Fall".
A few hundred years ago, The Fall was a common bottom-line assumption. And now that we don't agree with it, we are quite sure there is no truth in the notion, certainly nothing important that we should have to wrestle with.
Isn't that change itself an example?--the tracks of a Power at work among us?
Here is a new, widely-shared, tenacious gestalt of attitude and belief: that only what we can see is real. It has made itself thoroughly at home, as if it had always been the norm. There is no particular evidence supporting it and yet it maintains itself in human minds, setting the context of what we will think and what we will attempt, not needing to "possess" anyone by force because it so seldom comes to our attention, let alone our suspicion.
The notion of The Fall was equally unquestioned. One reason for George Fox's continual trouble with the authorities was his belief that he had been freed from the domination of Sin within this bodily life-- something they considered a blasphemous impossibility. But Fox agreed with them that sin afflicted the bulk of humanity, not only in their inequities and cruelties but in what we would consider their harmless amusements. Barclay, writing for non-Quakers--but with no evident disagreement from Fox or others--says:
"All Adam's posterity (or mankind), both Jew and Gentiles, as to the first Adam, or earthly man, is fallen, degenerated, and dead, deprived of the sensation or feeling of this inward testimony or seed of God, and is subject unto the power, nature, and seed of the serpent, which he sows in men's hearts, while they abide in this natural and corrupted state, from whence it comes, that not their words and deeds only, but all their imaginations, are evil perpetually in the sight of God, as proceeding from this depraved and wicked seed." [Apology pg 11]
I'm not calling this an accurate model of human nature, or one we should return to. There was a serious flaw in it, or rather in this half of the overall concept: the notion that there could be a human nature separate from God. Our connectedness to God was then tacked on, in the form of "Christ, who enlightens every man who comes into the world"--to explain the presence of everything good in us.
Unfortunately, this description still consigned "our own will" to the "natural and corrupted" side of things. "Quietism", the belief that we can best serve God by annihilation of everything "creaturely" about us, was consequently widespread among Friends for over a hundred years.
Fenelon, a Catholic mystic of the time, was an influential example of such thinking. Although his letters reveal him as a wise, gently humorous and compassionate spiritual adviser, his theology was bound by the same harsh judgment of all things merely human: "Let [God] do as He sees fit with you. Be content to obey His will in all things, and to merge your will concerning everything in His. What right have you, who are not your own, to any intrinsic possession? A slave has no proprietary rights, how much less the creature which in itself is mere sin and nothingness, and which can possess nought save by the gift of God?" [The Royal Way of the Cross,tr H. Sidney Lear, 1980, The Community of Jesus, Inc. Orleans, MA 02633 pg 160]
John Woolman was no less a Quietist: "In true silence strength is renewed, and the mind is weaned from all things save as they may be enjoyed in the divine will; and a lowliness in outward living, opposite to worldly honour, becomes truly acceptable to us. In the desire after outward gain, the mind is prevented from a perfect attention to the voice of Christ; yet being weaned from all things, except as they may be enjoyed in the divine will, the pure light shines into the soul. Where the fruits of the spirit which is of this world are brought forth by many who profess to be led by the Spirit of truth, and cloudiness is felt to be gathering over the visible Church, the sincere in heart, who abide in true stillness, and are exercised therein before the Lord for His name's sake, have knowledge of Christ in the fellowship of His sufferings; and inward thankfulness is felt at times, that through Divine love our own wisdom is cast out, and that forward, active part in us is subjected, which would rise and do something without the pure leadings of the spirit of Christ."
In the midst of a highly-effective campaign for an issue that intensely concerned him--persuading American Friends to free their slaves--he says: "I was deeply engaged in inward cries to the Lord for help, that I might stand wholly resigned, and move only as He might be pleased to lead me."
Later, in a time of sickness, he "heard a soft melodious voice, more pure and harmonious than any I had heard with my ears before; I believed it was the voice of an angel who spake to the other angels; the words were, 'John Woolman is dead.' " When he thought about it, he gratefully concluded that the words "meant no more than the death of my own will."
Is our "own will" necessarily opposed to God's? We have all experienced collisions between God's will and our own-- and would prefer this to happen less often-- but how could anything in this creation be entirely separate from God?
There is merit in the Quietist program to avoid being enslaved to our capricious personal wants and errors, but not in the assumptions used to justify it.
Some sayings attributed to Jesus could suggest an ethic of self-annihilation, but they aren't consistent with the teaching that God is our loving Father. Would God crush the wills he gave us?-- or would he guide those wills toward wanting our true good? These quotes, I think, were misinterpreted in a spirit better suited to earlier times--not the Spirit of Modernism that so befuddles modern Americans, but a different Power, pretending to absolute truth and unlimited authority as these things characteristically do.
Aren't I arbitrarily adopting one notion from the Christian tradition--the Powers--and dismissing a related notion, The Fall? No, I find some truth in both, and want to bring that truth into this present milieu, so different and so much like the one where they developed.
I say that a bible such as the Hebrew Scriptures, the Christian Bible, or the Koran--is itself a principality of great power, whether for good and for misuse. (Consider how Romans 13: "Be subject to the governing authorities"--was once used by German churches to blind and paralyze themselves in the face of the Nazi regime.) Such things are not given to render us foolproof or to ossify our prejudices, but rather to help us find truths we might otherwise miss in the routine course of our lives.