What follows is merely a collection of quotations from Thomas Aquinas dedicated to the topic of the equality of the three persons of the Trinity. Aquinas is one of my subsidiary interests. He is a systematic and (needless to say) deep writer. This is to say that I need more time and reading in order to expound further without sounding repetitive. However, one thing seems clear to me: one of Aquinas' intentions is to avoid and/or reject the ancient error of subordinationism.
Compendium of Theology, Chapter 43 (The Divine Word not Distinct from the Father in Time, Species, or Nature): "Among things that are not distinct in essence, there can be no distinction according to species, time, or nature. Therefore, since the Word is consubstantial with the Father, He cannot differ from the Father in any of these respects. There can be no difference according to time. The divine Word is present in God for the reason that God understands Himself, thereby conceiving His intelligible Word. Hence, if at any time there were no Word of God, during that period God would not understand Himself. But God always understood Himself during His whole existence, for His understanding is His existence. Therefore His Word, also, existed always. And so in the rule of Catholic faith we say that the Son of God 'is born of the Father before all ages.'"
Summa Theologiae, Part 1, Q. 42 (Equality and Likeness Among the Divine Persons), A. 1 (Whether there is equality in God)): "We must needs admit equality among the divine persons. For, according to the Philosopher (Metaph. x, text 15,16, 17), equality signifies the negation of greater or less. Now we cannot admit anything greater or less in the divine persons; for as Boethius says (De Trin. i): "They must needs admit a difference [namely, of Godhead] who speak of either increase or decrease, as the Arians do, who sunder the Trinity by distinguishing degrees as of numbers, thus involving a plurality." Now the reason of this is that unequal things cannot have the same quantity. But quantity, in God, is nothing else than His essence. Wherefore it follows, that if there were any inequality in the divine persons, they would not have the same essence; and thus the three persons would not be one God; which is impossible. We must therefore admit equality among the divine persons."
Part 1, Q. 42, A. 2 (Whether the person proceeding is co-eternal with His principle, as the Son with the Father): "We must say that the Son is co-eternal with the Father. In proof of which we must consider that for a thing which proceeds from a principle to be posterior to its principle may be due to two reasons: one on the part of the agent, and the other on the part of the action. On the part of the agent this happens differently as regards free agents and natural agents. In free agents, on account of the choice of time; for as a free agent can choose the form it gives to the effect, as stated above (I:41:2), so it can choose the time in which to produce its effect. In natural agents, however, the same happens from the agent not having its perfection of natural power from the very first, but obtaining it after a certain time; as, for instance, a man is not able to generate from the very first. Considered on the part of action, anything derived from a principle cannot exist simultaneously with its principle when the action is successive. So, given that an agent, as soon as it exists, begins to act thus, the effect would not exist in the same instant, but in the instant of the action's termination. Now it is manifest, according to what has been said (I:41:2), that the Father does not beget the Son by will, but by nature; and also that the Father's nature was perfect from eternity; and again that the action whereby the Father produces the Son is not successive, because thus the Son would be successively generated, and this generation would be material, and accompanied with movement; which is quite impossible. Therefore we conclude that the Son existed whensoever the Father existed and thus the Son is co-eternal with the Father, and likewise the Holy Ghost is co-eternal with both."
Part 2, Q. 42, A. 4 (Whether the Son is equal to the Father in greatness): "The Son is necessarily equal to the Father in greatness. For the greatness of God is nothing but the perfection of His nature. Now it belongs to the very nature of paternity and filiation that the Son by generation should attain to the possession of the perfection of the nature which is in the Father, in the same way as it is in the Father Himself. But since in men generation is a certain kind of transmutation of one proceeding from potentiality to act, it follows that a man is not equal at first to the father who begets him, but attains to equality by due growth, unless owing to a defect in the principle of generation it should happen otherwise. From what precedes (I:27:2; I:33:3), it is evident that in God there exist real true paternity and filiation. Nor can we say that the power of generation in the Father was defective, nor that the Son of God arrived at perfection in a successive manner and by change. Therefore we must say that the Son was eternally equal to the Father in greatness. Hence, Hilary says (De Synod. Can. 27): 'Remove bodily weakness, remove the beginning of conception, remove pain and all human shortcomings, then every son, by reason of his natural nativity, is the father's equal, because he has a like nature.'"
Part 1, Q. 42, A. 6 (Whether the Son is equal to the Father in power): "The Son is necessarily equal to the Father in power. Power of action is a consequence of perfection in nature. In creatures, for instance, we see that the more perfect the nature, the greater power is there for action. Now it was shown above (Article 4) that the very notion of the divine paternity and filiation requires that the Son should be the Father's equal in greatness--that is, in perfection of nature. Hence it follows that the Son is equal to the Father in power; and the same applies to the Holy Ghost in relation to both."
The Compendium, though incomplete, is still a very helpful summary of Aquinas' theology, and I personally find it a great introduction to his thought (after perhaps his On Being and Essence). Summa Theologiae does not need any introduction. I will only say that, although I have reported here only a selection of quotations from 1:42, the entire section is very worth meditating.
©
Summa Theologiae, Part 1, Q. 42 (Equality and Likeness Among the Divine Persons), A. 1 (Whether there is equality in God)): "We must needs admit equality among the divine persons. For, according to the Philosopher (Metaph. x, text 15,16, 17), equality signifies the negation of greater or less. Now we cannot admit anything greater or less in the divine persons; for as Boethius says (De Trin. i): "They must needs admit a difference [namely, of Godhead] who speak of either increase or decrease, as the Arians do, who sunder the Trinity by distinguishing degrees as of numbers, thus involving a plurality." Now the reason of this is that unequal things cannot have the same quantity. But quantity, in God, is nothing else than His essence. Wherefore it follows, that if there were any inequality in the divine persons, they would not have the same essence; and thus the three persons would not be one God; which is impossible. We must therefore admit equality among the divine persons."
Part 1, Q. 42, A. 2 (Whether the person proceeding is co-eternal with His principle, as the Son with the Father): "We must say that the Son is co-eternal with the Father. In proof of which we must consider that for a thing which proceeds from a principle to be posterior to its principle may be due to two reasons: one on the part of the agent, and the other on the part of the action. On the part of the agent this happens differently as regards free agents and natural agents. In free agents, on account of the choice of time; for as a free agent can choose the form it gives to the effect, as stated above (I:41:2), so it can choose the time in which to produce its effect. In natural agents, however, the same happens from the agent not having its perfection of natural power from the very first, but obtaining it after a certain time; as, for instance, a man is not able to generate from the very first. Considered on the part of action, anything derived from a principle cannot exist simultaneously with its principle when the action is successive. So, given that an agent, as soon as it exists, begins to act thus, the effect would not exist in the same instant, but in the instant of the action's termination. Now it is manifest, according to what has been said (I:41:2), that the Father does not beget the Son by will, but by nature; and also that the Father's nature was perfect from eternity; and again that the action whereby the Father produces the Son is not successive, because thus the Son would be successively generated, and this generation would be material, and accompanied with movement; which is quite impossible. Therefore we conclude that the Son existed whensoever the Father existed and thus the Son is co-eternal with the Father, and likewise the Holy Ghost is co-eternal with both."
Part 2, Q. 42, A. 4 (Whether the Son is equal to the Father in greatness): "The Son is necessarily equal to the Father in greatness. For the greatness of God is nothing but the perfection of His nature. Now it belongs to the very nature of paternity and filiation that the Son by generation should attain to the possession of the perfection of the nature which is in the Father, in the same way as it is in the Father Himself. But since in men generation is a certain kind of transmutation of one proceeding from potentiality to act, it follows that a man is not equal at first to the father who begets him, but attains to equality by due growth, unless owing to a defect in the principle of generation it should happen otherwise. From what precedes (I:27:2; I:33:3), it is evident that in God there exist real true paternity and filiation. Nor can we say that the power of generation in the Father was defective, nor that the Son of God arrived at perfection in a successive manner and by change. Therefore we must say that the Son was eternally equal to the Father in greatness. Hence, Hilary says (De Synod. Can. 27): 'Remove bodily weakness, remove the beginning of conception, remove pain and all human shortcomings, then every son, by reason of his natural nativity, is the father's equal, because he has a like nature.'"
Part 1, Q. 42, A. 6 (Whether the Son is equal to the Father in power): "The Son is necessarily equal to the Father in power. Power of action is a consequence of perfection in nature. In creatures, for instance, we see that the more perfect the nature, the greater power is there for action. Now it was shown above (Article 4) that the very notion of the divine paternity and filiation requires that the Son should be the Father's equal in greatness--that is, in perfection of nature. Hence it follows that the Son is equal to the Father in power; and the same applies to the Holy Ghost in relation to both."
The Compendium, though incomplete, is still a very helpful summary of Aquinas' theology, and I personally find it a great introduction to his thought (after perhaps his On Being and Essence). Summa Theologiae does not need any introduction. I will only say that, although I have reported here only a selection of quotations from 1:42, the entire section is very worth meditating.
©
