Objection 1. It would seem that the name 'Word' does not import relation to creatures. For every name that connotes some effect in creatures, is said of God essentially. But Word is not said essentially, but personally. Therefore Word does not import relation to creatures.
Objection 2. Further, whatever imports relation to creatures is said of God in time; as "Lord" and "Creator." But Word is said of God from eternity. Therefore it does not import relation to the creature.
Objection 3. Further, Word imports relation to the source whence it proceeds. Therefore, if it imports relation to the creature, it follows that the Word proceeds from the creature.
Objection 4. Further, ideas (in God) are many according to their various relations to creatures. Therefore if Word imports relation to creatures, it follows that in God there is not one Word only, but many.
Objection 5. Further, if Word imports relation to the creature, this can only be because creatures are known by God. But God does not know beings only; He knows also non-beings. Therefore in the Word are implied relations to non-beings; which appears to be false.
On the contrary, Augustine says (QQ. lxxxiii, qu. 63), that "the name Word signifies not only relation to the Father, but also relation to those beings which are made through the Word, by His operative power."
I answer that, Word implies relation to creatures. For God by knowing Himself, knows every creature. Now the word conceived in the mind is representative of everything that is actually understood. Hence there are in ourselves different words for the different things which we understand. But because God by one act understands Himself and all things, His one only Word is expressive not only of the Father, but of all creatures.
And as the knowledge of God is only cognitive as regards God, whereas as regards creatures, it is both cognitive and operative, so the Word of God is only expressive of what is in God the Father, but is both expressive and operative of creatures; and therefore it is said (Psalm 32:9): "He spake, and they were made;" because in the Word is implied the operative idea of what God makes.
Reply to Objection 1. The nature is also included indirectly in the name of the person; for person is an individual substance of a rational nature. Therefore the name of a divine person, as regards the personal relation, does not imply relation to the creature, but it is implied in what belongs to the nature. Yet there is nothing to prevent its implying relation to creatures, so far as the essence is included in its meaning: for as it properly belongs to the Son to be the Son, so it properly belongs to Him to be God begotten, or the Creator begotten; and in this way the name Word imports relation to creatures.
Reply to Objection 2. Since the relations result from actions, some names import the relation of God to creatures, which relation follows on the action of God which passes into some exterior effect, as to create and to govern; and the like are applied to God in time. But others import a relation which follows from an action which does not pass into an exterior effect, but abides in the agent--as to know and to will: such are not applied to God in time; and this kind of relation to creatures is implied in the name of the Word. Nor is it true that all names which import the relation of God to creatures are applied to Him in time; but only those names are applied in time which import relation following on the action of God passing into exterior effect.
Reply to Objection 3. Creatures are known to God not by a knowledge derived from the creatures themselves, but by His own essence. Hence it is not necessary that the Word should proceed from creatures, although the Word is expressive of creatures.
Reply to Objection 4. The name of Idea is imposed chiefly to signify relation to creatures; and therefore it is applied in a plural sense to God; and it is not said personally. But the name of Word is imposed chiefly to signify the speaker, and consequently, relation to creatures, inasmuch as God, by understanding Himself, understands every creature; and so there is only one Word in God, and that is a personal one.
Reply to Objection 5. God's knowledge of non-beings and God's Word about non-beings are the same; because the Word of God contains no less than does the knowledge of God, as Augustine says (De Trin. xv, 14). Nevertheless the Word is expressive and operative of beings, but is expressive and manifestive of non-beings.
Source: Summa Theologica (New Advent)