FIRST ARTICLE: WHETHER THE DIVINE PERSONS ARE EQUAL

Reply. The reply is affirmative and of faith according to the Athanasian Creed, which professes that the divine persons are "coequal, " and the same doctrine is defined by many councils.[572] In the Scriptures it is said of the Son, "Who being in the form of God, thought it not robbery to be equal with God."[573] The explanation given in the body of the article is this: things are said to be unequal according to a difference in quantity. But in God quantity is the perfection of divine nature, which is numerically the same in the three persons. Therefore the three persons are not unequal but all three are coequal.

In the reply to the first difficulty, St. Thomas explains that quantity is twofold: quantity of amount (molis) and quantity of power (virtutis). The latter is predicated according to perfection of nature or form. To be one in nature is to be the same; to be one in quantity is to be equal; and to be one in quality is to be similar.[574] Corollaries are presented in the following articles.

In the reply to the second difficulty, it is noted that the three persons are similar because we have here equality not of amount but of power, according to communication in one form.