The philosophical statements of the doctrine of the Trinity have been intended by their authors either to prove it, or to illustrate it, or to explain it away and substitute some speculative theory as to the constitution of the universe for the Scriptural doctrine of the Triune God. The two former of these classes, those designed for proof, and those designed for illustration, need not be discriminated. It may be remarked in reference to them all that they are of little value. They do not serve to make the inconceivable intelligible. The most they can do, is to show that in other spheres and in relation to other subjects, we find a somewhat analogous triplicity in unity. In most cases, however, these illustrations proceed on the assumption that there are mysteries in the Godhead which have no counterpart in the constitution of our nature, or in anything around us in the present state of our existence.
We have already seen that the fathers were accustomed to refer to the union of light, heat, and radiance in the one substance of the sun; to a fountain and its streams; to the root, stem, and flower of a plant; to the intellect, will, and affections in the soul; as examples of at least a certain kind of triplicity in unity, elsewhere than in the Godhead. The last-mentioned analogy, especially, was frequently presented, and that in different forms. Augustine said, that as man was made in the image of the Triune God, we have reason to expect something in the constitution of our nature answering to the Trinity in the Godhead. He refers to the memory, intelligence, and will, as co-existing in one mind, so that the operations of the one are involved in the operations of the others. Gregory of Nyssa refers for his illustration to the soul, the reason, and the living power, united in one spiritual substance in man. It was admitted, however, that these analogies did not hold as to the main point, for these different powers in man are not different subsistences, but different modes of activity of one and the same personal essence, so that these illustrations lead rather to the Sabellian, than to the Scriptural view of the doctrine of the Trinity.
By far the most common illustration was borrowed from the operations of our consciousness. We conceive of ourselves as objective to ourselves, and are conscious of the identity of the subject and object. We have thus the subjective Ego, the objective Ego, and the identity of the two; the desired Thesis, Analysis, and Synthesis. In one form or another, this illustration has come down from the fathers, through the schoolmen and reformers, to theologians of our own day. Augustine1 says, “Est quædam imago Trinitatis, ipsa mens, et notitia ejus, quod est proles ejus ac de seipsa verbum ejus, et amor tertius, et hæc tria unum atque una substantia.” Again,2 “Hæc — tria, memoria, intelligentia, voluntas, quoniam non sunt tres vitæ, sed una vita; nec tres mentes, sed una mens: consequenter utique nec tres substantiæ sunt, sed una substantia.” And,3 “Mens igitur quando cogitatione se conspicit, intelligit se et recognoscit: gignit ergo hunc intellectum et cognitionem suam… . . Hæc autem duo, gignens et genitum, dilectione tertia copulantur, quæ nihil est aliud quam voluntas fruendum aliquid appetens vel tenens.” Anselm4 has the same idea: “Habet mens rationalis, quum se cogitando intelligit, secum imaginem suam ex se natam, id est cogitationem sui ad suam similitudinem, quasi sua impressione formatam, quamvis ipsa se a sua imagine, non nisi ratione sola, separare possit, quæ imago ejus verbum ejus est. Hoc itaque modo, quis neget, summam sapientem, quum se dicendo intelligit, gignere consubstantialem sibi similitudinem suam, id est Verbum suum.” Melancthon5 adopts and carries out the same idea: “Filius dicitur imago et λόγος: est igitur imago cogitatione Patris genita; quod ut aliquo modo considerari possit, a nostra mente exempla capiamus. Voluit enim Deus in homine conspici vestigia sua… . . Mens humana cogitando mox pingit imaginem rei cogitatæ, sed nos non transfundimus nostram essentiam in illas imagines, suntque cogitationes illæ subitæ et evanescentes actiones. At Pater æternus sese intuens gignit cogitatonem sui, quæ est imago ipsius, non evanescens, sed subsistens, communicata ipsi essentia. Hæc igitur imago est secunda persona… . . Ut autem Filius nascitur cogitatione, ita Spiritus Sanctus procedit a voluntate Patris et Filii; voluntatis enim est agitare, diligere, sicut et cor humanam non imagines, sed spiritus seu halitus gignit.” Leibnitz,6 says “Je ne trouve rien dans les créatures de plus propre à illustrer ce sujet, que la réflexion des espirits, lorsqu’un même esprit est son propre objet immediat, et agit sur soi-même en pensant à soi-même et à ce qu’il fait. Car le redoublement donne une image ou ombre de deux substances respectives dans une même substance absolue, savoir de celle qui entend, et de celle qui est entendue; l’un et l’autre de ces êtres est substantiel, l’un et l’autre est un concret individu, et ils différent par des rélations mutuelles, mais ils ne sont qu’une seule et même substance individuelle absolue.”