146. It needs to be known that a completely chaste or pure conjugial love does not exist among human beings, and not among angels either. There is always something not chaste or pure, which attaches itself or trails from it. But this is the product of a different nature from that which is the source of unchastity. For in these cases what is chaste is above and what is not chaste is below, and the Lord puts between them something like a hinged door, which is opened by the way thought is directed. Care is taken to prevent it staying open, so that one can pass into the other and become mixed. For a person's natural level is from birth infected and filled with evils; not so his spiritual level, because this comes to birth by the Lord's doing, since it is regeneration; and this is a process of progressive separation from the evils which are by birth attached to his propensities. No love, either among men or among angels, is completely pure, for this is impossible; but the end in view, the aim or intention of the will, is what is primarily considered by the Lord; and therefore to the extent that a person is devoted to these aims and perseveres in them, so far is he set on the road to purity, and so far does he advance towards it as he develops. On this see 71 above.