Ver. 231. Virtuous and vicious ev'ry man must be,] There is yet a third cause of this error of no vice, no virtue, composed of the other two, i.e. partly speculative, and partly practical. And this also the poet considers, from ver. 230 to 239, showing it ariseth from the imperfection of the best characters, and the inequality of all; whence it happens that no man is extremely virtuous or vicious, nor extremely constant in the pursuit of either. Why it so happens, the poet informs us, who with admirable sagacity assigns the cause in this line:
For, vice or virtue, self directs it still.
An adherence or regard to what is, in the sense of the world, a man's own interest, making an extreme, in either, almost impossible. Its effect in keeping a good man from the extreme of virtue needs no explanation; and, in an ill man, self-interest showing him the necessity of some kind of reputation, the procuring and preserving that will necessarily keep him from the extreme of vice.
Ver. 239. That counterworks each folly and caprice;] The mention of this principle, that self directs vice and virtue, and its consequence, which is, that
Each individual seeks a sev'ral goal,
leads the author to observe,
That heav'n's great view is one, and that the whole.
And this brings him naturally round again to his main subject, namely, God's producing good out of ill, which he prosecutes from ver. 238 to 249.
Ver. 249. Heav'n forming each on other to depend,] I. Hitherto the poet hath been employed in discoursing of the use of the passions, with regard to society at large; and in freeing his doctrine from objections. This is the first general division of the subject of this epistle.
II. He comes now to show, from ver. 248 to 261, the use of these passions, with regard to the more confined circle of our friends, relations, and acquaintance; and this is the second general division.