"On the twofold sense of the soul."

Now the rational soul was on this account equipped with a twofold sense, that it might grasp visible things without through the flesh, and invisible things within through reason, so that both visible and invisible things might excite it to praise of the Creator. For God would not be praised in all His works by the rational creature, if all the works of God were not known by the rational creature. Therefore, that the praise of God might be perfect, the works of God were shown to the rational creature, so that it might admire Him within and without, and through admiration advance to love.

One creature was made whose sense was wholly within, and another creature was made whose sense was wholly without. The sense of the angels was within, and the sense of brute animals was without. [...] And man was placed in a middle position, that he might have sense within and without; within for invisible things, without for visible; within through the sense of reason, without through the sense of flesh, that he might go in and contemplate, and might go out and contemplate; that he might have wisdom within, the works of wisdom without, that he might contemplate both, and be refreshed from both, see and rejoice, love and praise. Wisdom was a pasture within within; the work of wisdom was a pasture without. And the sense of man was permitted to go to both, and find refreshment in both, to go by cognition, to be refreshed by love.

Wisdom was a book written within; the work of wisdom a book written without. But He willed afterwards that it still be written otherwise without, that wisdom might be seen more manifestly and recognized more perfectly, that the eye of man might be illumined to the second writing, since it had been darkened to the first. Therefore, He made a second work after the first, and that was more evident, since it not only pointed out but illumined. He assumed flesh not losing divinity, and was placed as a book written within and without; in humanity without, within in divinity, so that it might be read without through imitation, within through contemplation; without unto health, within unto felicity; without unto merit, within unto joy. Within, "In the beginning was the Word,"" (John 1:1); without, "the Word became flesh and dwelt among us," (John 1:14).

- Hugh of St. Victor, De Sacramentis Book One, Part Six, Chapter V