In that state of internal experience, which is described by Madam Guyon, there seems to be a perfect balance and harmony of the different parts of the mind. There may be deep feeling, (and there is in reality very deep feeling,) but it is so perfectly controlled by a sense of union with the will of God, that the result is complete simplicity and rest of soul. Just as it is in a piece of complicated machinery. If the wheels and other parts are out of order, or if there is much friction, the action of the machinery is perplexed and is really weak, although there is exceedingly great jarring and discordant noise. But when the wheels are all in position, and there is no friction, the action may be one of tremendous power, and yet so easy and quiet as to be hardly perceptible. And such is the true kingdom of God in the soul. It comes and exists with power, but with great simplicity. There is nothing in it, in itself considered, which is calculated to attract and secure worldly observation. It is mighty; but like God himself, it is inwardly silent, "a still, small voice."
The religiously quiet man, that is to say, the man who is inwardly and truly subdued and quiet in consequence of religion, is really the man of great religious strength; and yet this strength, in consequence of that harmonious silence of movement, which is the result of its own perfection, is so hidden from his view, that he seems to be hardly conscious of its existence. But it is very different with the natural man; and also with the Christian, who still retains a large infusion of the natural element. While the operations of the sanctified man are harmonious and quiet, and, therefore, are withdrawn, in a great measure, from distinct inward notice; those of the natural mind are not only self-interested, but are restless, impetuous, and contradictory; and, therefore, as a matter of course are mentally prominent and perceptible. The true controlling principle of the mind, in the case of the natural man, is gone; and its parts in action strike and jar upon each other with an inward concussion, like the hinges of the gates of Hell, that grate "harsh thunder."
— edited from The Interior or Hidden Life (2nd edition, 1844) Part 3, Chapter 11.