Chapter 53 — That the relations whereby Father, Son, and Holy Spirit are distinguished are real, and not merely rational

The relations by which the Father, the Son, and the Holy Spirit are distinguished from one another are real relations, and not merely rational. Those relations are purely rational which do not follow from anything found in the nature of things, but follow from intellectual apprehension alone. Thus right and left in a stone are not real relations, but only rational relations; they do not follow from any real disposition present in the stone, but only from the perception of one who apprehends the stone as left because it is to the left of some animal. On the other hand, left and right in an animal are real relations, because they follow on certain dispositions found in definite parts of the animal. Accordingly, since the relations whereby the Father and the Son and the Holy Spirit are distinguished really exist in God, the aforesaid relations must be real relations, and are not merely relations of reason.