And let none of my Readers be angry or think themselves ill used, when I tell them the Devil may be in them, and may act them, and by them, and they not know it; for I must add, it may, perhaps, be one of the greatest Pieces of human Wisdom in the World, for a Man to know when the Devil is in him, and when not; when he is a Tool and Agent of Hell, and when he is not; in a Word, when he is doing the Devil's Work, and under his Direction, and when not. It is true, this is a very weighty Point, and might deserve to be handled in a more serious Way than I seem to be talking in all this Book; but give me leave to talk of Things my own way, and withall, to tell you, that there is no Part of this Work so seemingly ludicrous, but a grave and well weigh'd Mind may make a serious and solid Application of it, if they please; nor is there any Part of this Work, in which a clear Sight and a good Sense may not see that the Author's Design is, that they should do so; and as I am now so near the End of my Book, I thought it was meet to tell you so, and lead you to it as far as I can. I say, 'tis a great Part of human Wisdom to know when the _Devil_ is acting in us and by us, and when not; the next and still greatest Part would be to prevent him, put a Stop to his Progress, bid him go about his Business, and let him know he should carry on his Designs no farther in that manner; that we will be his Tools no longer; in short, to turn him out of Doors, and bring a stronger Power to take Possession; but this, indeed, is too solid a Subject, and too great to begin with here. But now, as to the bare knowing when he is at work with us, I say this, tho' it is considerable, may be done, nor is it so very difficult; _for Example_, you have no more to do but look a little into the Microcosm of the Soul, and see there how the Passions which are the Blood, and the Affections which are the Spirit, move in their particular Vessels; how they circulate, and in what Temper the Pulse beats there, and you may easily see who turns the Wheel; if a perfect Calm possesses the Soul; if Peace and Temper prevail, and the Mind feels no Tempests rising; if the Affections are regular and exalted to vertuous and sublime Objects, the Spirits cool, and the Mind sedate, the Man is in a general Rectitude of Mind, he may be truly said to be _his own Man_; Heaven shines upon his Soul with its benign Influences, and he is out of the Reach of the evil Spirit; for the divine Spirit is an Influence of Peace, all calm and bright, happy and sweet like it self, and tending to every Thing that is good both present and future.