The wisdom of the Divine Artist is, as the poet finely observes, very illustrious in this contrivance; for the mind and body having now one common interest, the efforts of virtue will have their force infinitely augmented:
'Tis thus the mercury, &c.
Ver. 197. Reason the bias, &c.] But lest it should be objected that this account favours the doctrine of necessity, and would insinuate that men are only acted upon, in the production of good out of evil; the poet teacheth, from ver. 196 to 203, that man is a free agent, and hath it in his power to turn the natural passions into virtues or into vices, properly so called:
Reason the bias turns to good from ill,
And Nero reigns a Titus, if he will.
Secondly, if it should be objected, that though he doth, indeed, tell us some actions are beneficial and some hurtful, yet he could not call those virtuous, nor these vicious, because, as he hath described things, the motive appears to be only the gratification of some passion, give me leave to answer for him, that this would be mistaking the argument, which, to ver. 249 of this epistle, considers the passions only with regard to society, that is, with regard to their effects rather than their motives: That, however, it is his design to teach that actions are properly virtuous and vicious; and though it be difficult to distinguish genuine virtue from spurious, they having both the same appearance, and both the same public effects, yet that they may be disentangled. If it be asked, by what means? he replies, from ver. 202 to 205, by conscience;—the God within the mind;—and this is to the purpose; for it is a man's own concern, and no one's else, to know whether his virtue be pure and solid; for what is it to others, whether this virtue (while, as to them, the effect of it is the same) be real or imaginary?
Ver. 205. Extremes in nature equal ends produce, &c.] But still it will be said, Why all this difficulty to distinguish true virtue from false? The poet shows why, from ver. 204 to 211, that though indeed vice and virtue so invade each other's bounds, that sometimes we can scarce tell where one ends and the other begins, yet great purposes are served thereby, no less than the perfecting the constitution of the whole, as lights and shades, which run into one another insensibly in a well-wrought picture, make the harmony and spirit of the composition. But on this account to say there is neither vice nor virtue, the poet shows, from ver. 211 to 217, would be just as wise as to say, there is neither black nor white, because the shade of that, and the light of this, often run into one another, and are mutually lost:
Ask your own heart, and nothing is so plain;
'Tis to mistake them, costs the time and pain.
This is an error of speculation, which leads men so foolishly to conclude, that there is neither vice nor virtue.
Ver. 217. Vice is a monster, &c.] There is another error, an error of practice, which hath more general and hurtful effects; and is next considered, from ver. 216 to 221. It is this, that though, at the first aspect, vice be so horrible as to fright the beholder, yet, when by habit we are once grown familiar with her, we first suffer, and in time begin to lose the memory of her nature, which necessarily implies an equal ignorance in the nature of virtue. Hence men conclude that there is neither one nor the other.
Ver. 221. But where th' extreme of vice, &c.] But it is not only that extreme of vice which stands next to virtue, which betrays us into these mistakes. We are deceived too, as he shows us, from ver. 220 to 231, by our observations concerning the other extreme. For, from the extreme of vice being unsettled, men conclude that vice itself is only nominal, at least rather comparative than real.