The reason is that their souls cannot fail to be out of harmony. For the soul of the one is open to receive conjugial love, while that of the other is shut for this purpose. It is shut in the case of the one who lacks religion, open for the one who has some religion. So at this level living together is quite impossible; and when conjugial love is banished thence, coldness arises, but this is in the case of the one who has no religion. There is no way this coldness can be dispelled, except by accepting a form of religion which matches the other's, if it is a true one. Otherwise the one without religion suffers a coldness which comes down from the soul into the body, even as far as the surface of the skin. This eventually makes him unable to look his partner in the eye, or to converse so that their breaths mix, and only in a voice which sounds remote; or to touch each other with the hand, and only with difficulty with the back. Not to mention the follies which this coldness allows to creep into the thoughts, which they do not reveal. This is why such marriages break up of their own accord. Moreover, it is well known that impious people have no respect for their partner; and all without religion are impious.