"And he also added, that she should bring forth his brother." Genesis iv. 2. The addition of one thing is a taking away of some other; as for instance, of particles in arithmetic, and of reasons in the soul. If then we must say that Abel is added, we must also think that Cain is taken away. But that the unusual character of expression may not cause perplexity to many we will endeavour to explain accurately the philosophy which is apparent beneath them, as clearly as may be in our power.
 It happens then, that there are two opinions contrary to and at variance with one another; the one of which commits everything to the mind as the leader of all reasoning, or feeling, or moving, or being stationary; and the other, attributing to God all the consequent work of creation as his own. Now the symbol of the former of these is Cain, which name, being interpreted means, "possession," from his appearing to possess all things; and the symbol of the other is Abel; for this name, being interpreted, means "referring to God." Now both these opinions were brought forth by one soul. But it follows of necessity that as soon as they were born they must have been separated; for it was impossible for enemies to dwell together for ever. Until then the soul brought forth the God-loving doctrine Abel, the self-loving Cain dwelt with her. But when she brought forth Abel, or unanimity with God, she abandoned unanimity with that mind which was wise in its own conceit.
 And this will be more evidently shown by the oracle which was given to Perseverance, that is to Rebecca; Genesis xxv. 24. for she also, having conceived the two inconsistent natures of good and evil, and having considered each of them very deeply
 Genesis iv. 2. 
 Genesis xxv. 24. 
 
according to the injunctions of prudence, beholding them both exulting, and making a sort of skirmish as a prelude to the war which was to exist between them; she, I say, besought God to explain to her what this calamity meant, and what was the remedy for it. And he answered her inquiry, and told her, "Two nations are in thy womb." This calamity is the birth of good and evil. "But two peoples shall be divided in thy bowels." And the remedy is, for these two to be parted and separated from one another, and no longer to abide in the same place.
 God therefore having added the good doctrine, that is Abel, to the soul, took away from it evil doctrine, that is Cain: for Abraham also, leaving mortal things, "is added to the people of God," Genesis xxv. 8. having received immortality, and having become equal to the angels; for the angels are the host of God, being incorporeal and happy souls. And in the same manner Jacob, the practiser of virtue, is added to the better one, Genesis xlix. 33. because he had quitted the worse.