There are inward and outward likenesses and unlikenesses. The inward ones are due solely to religion, for it is this which is implanted in souls, and by means of souls is transmitted by parents to children, as the highest kind of inclination. For the soul of each individual draws life from the marriage of good and truth, and this is the source of the church. Since this is different and varied in different parts of the world, the souls of all human beings are also different and varied. Inward likenesses and unlikenesses are therefore from this source, and the linking of married couples depends upon these, as has been said.

[2] Outward likenesses and unlikenesses are not of souls, but of characters. I mean by characters affections and the outward inclinations arising from them; these are principally introduced after birth by upbringing, the company kept, and the habits these lead to. For we say, 'I have a mind to do this or that,' which implies an affection or inclination towards it. False ideas adopted about one or another life-style can also often form characters; this is the reason for inclinations towards marriage with ill-matched partners, and for rejecting marriage with well-matched partners. But still these marriages, when the couple has been living together for some time, undergo changes depending on the likenesses and unlikenesses resulting from heredity and at the same time from upbringing; and unlikenesses cause coldness.

[3] It is the same with unlikeness in behaviour, as, for instance, a coarse man or woman with an refined woman or man, a cleanly man or woman with a dirty one, a quarrelsome one with a peaceable one, in short, an inconsiderate one with a considerate one. Marriages between such unlike persons are not unlike the pairings of animals of different species, such as sheep and goats, deer and mules, hens and geese, sparrows and noble birds, even indeed between dogs and cats, which are too unlike to pair. But in the human race the face does not indicate unlikeness, but habits; these therefore lead to coldness.