The doctrine states that God is completely unchangeable.
Already at the Council of Nicaea, anyone who says that the Son of God is changeable (against the Arians) is excommunicated. Similarly, at the Fourth Lateran and the First Vatican Council ("God is an unchangeable spiritual entity"). Opponents include not only the Arians but also pantheists, Gnostics, and even Orthodox Protestants, partly for supposed religious-moral interests: God changes His previous condemnatory attitude towards the penitent; and partly in the manner of the Arians: The Incarnate Word, in order to be a real human, renounces the excellences of his divinity, empties himself. The modern-day Jehovah's Witnesses also deny this, they have a deeply anthropomorphic image of God. They initially interpret the name YHWH as "I Will Become What I Choose to Become" or "He Causes to Become". The Watchtower's interpretation of the YHWH name comes from a Hebrew verb that means “to become" (ha·wah). However, it actually comes from the verb "yahway," which means "to be," "to exist." The Hebrew Bible explains it by the formula 'Ehye ašer ehye' ("I Am that I Am"). The word אֶהְיֶה (’Ehyeh) is the first person singular imperfective form of הָיָה (hayah), 'to be'. So, God does not "become" anything, since he does not change. The Watchtower's image of God is anthropomorphic: He has a body, he literally dwells in the sky, he is not innately omniscient but has the "capability" to foresee "the future" if he so desires.
In fact God is the actuality of every actuality (or pure Act, actus purus) and the perfection of all perfections. God's immutability also follows from God's simplicity: He is the completion of existence (actus purus), therefore there is no potential existence in him that would still be waiting for unfolding or realization, likewise, he cannot lose anything. His existence and everything he possesses are with eternal necessity, and it could not be otherwise. He cannot gain anything new, neither in knowledge nor in value. His outward acts do not change Him either. The act of creation in Him is such a free act that has always been in Him, is one with his essence, and has its temporal effect outwardly. When he communicates himself in grace, it is not he who changes, but man enters into a new relationship with him and perceives his supernatural effects. The mystery of the Incarnation must be understood in the same way. It was not the deity or personality of the Son that changed, but the humanity of Christ entered into a unique relationship with him.
a) The Scripture generally states that God is always identical with Himself, unlike the creatures: "In the beginning, O Lord, thou foundedst the earth: end the heavens are the works of thy hands. They shall perish but thou remainest: and all of them shall grow old like a garment: And as a vesture thou shalt change them, and they shall be changed. But thou art always the selfsame, and thy years shall not fail." (Psalm 102:25-27) "Every best gift, and every perfect gift, is from above, coming down from the Father of lights, with whom there is no change, nor shadow of alteration." (τροπὴς ἀποσκίασμα, James 1:17) Cyril of Alexandria comments on this: "But what else would it be than change and gross variability, if God were to migrate from potency to actuality?" (Cyr. Al. Dial. ad. ar. 2.) The Scripture even identifies the metaphysical basis of unchangeability: "I am the Lord, and I do not change". (Malachi 3:6; cf. Augustine, Sermo 7:7)
b) However, Scripture, more often in its usual method of discussion, concretely and in detail describes God's immutability in His individual actions and positions: "God is not a man, that he should lie, nor as the son of man, that he should be changed." (Numbers 23:19) "Though she remains the same, she renews everything." (Wisdom 7:27; cf. Sirach 42:16.) The Lord's plan remains forever, His heart's intent from generation to generation". (Psalm 33:11; cf. 1 Samuel 15:29, Proverbs 19:21) God alone is uncorruptible and immortal. (Romans 1:23, 1 Timothy 1:17, 6:16, Psalm 35:10)
Therefore, the strong anthropomorphisms and anthropopathisms of Scripture, especially the Old Testament (God shows anger, regret, etc., Genesis 6:6, Psalm 106:40, Hosea 1:6, etc.), must be measured and adjusted to the basic truth of faith of God's unchangeability. These, i.e., are spoken not because of the similarity of the observable effect to the emotion. Therefore, "God regretted making man" means: what God did because of the degradation of people shows effects like when people regret their actions. The church fathers specifically defend the unchangeability of God against the Arians, who distinguished the changeable Son from the unchangeable Father; against the Gnostics, who argue that God creates the world of spirits through emanations emitted from His own essence; and against the Stoics, who attribute emotions, passions, especially anger, to God; finally against the Patripassians. (See especially Tertullian, Prax. 17; Augustine, Civ. Dei XI 10 k.; XII 17, 2; Conf. XII 7; in Jn 23, 9.)
Reason thus concludes:
a) God is utterly simple. But what changes is essentially complex, at least metaphysically; because if change occurs, something remains and something else becomes (quidquid mutatur, quantum ad aliquid manet, quantum ad aliquid transit).
b) God is infinitely perfect. But what changes either gains or loses perfection; therefore, it is not the most perfect.
c) God is self-existing. However, what changes is changed by something else; therefore, the changer in his change is not self-existing but from something else. The first proof of God of Thomas Aquinas, infers the first unchangeable cause from the changing being (primum movens immobile). Denying or obscuring God's unchangeability falsifies the Catholic conception of God and sooner or later leads to monism; if God is changeable, then He is not wholly transcendent, but shares with that world which shares in its most noticeable property, changeability. A question arises here: If God is unchangeable, how does He change the things? According to Aristotle, God as a final cause moves the world: by attracting the spiritual heaven (the primum mobile) directly as a goal, which then communicates its movement to the other heavens and ultimately to the earthly beings; however, it itself remains motionless and inactive. According to Plato and the Platonic school of thought, in spite of His immutability, God as an absolute fullness of being is also absolute and constant activity. This is also the understanding of revelation: "Wisdom is quicker than any motion… she is one, yet can do all things; remaining in herself, she renews all things". (Wisdom 7:24–27) Here is the main weakness of Aristotle's conception of God.
Difficulties.
1. God is free in the creation, governance, salvation of the world, and in the establishment of the supernatural order of existence. But if He is free, He could establish another world and world order, and could govern the existing one differently. Therefore, He is changeable (at least in thought: He could change His intentions); or else, He is not free.
Solution: The essence of freedom is to take a stand based purely on the real value of things, excluding all foreign perspectives and influences not related to the matter. The more the decision is based on the actual value of things and the more full of mental energy it is, the freer it is; changeability is not essential; after all, the highest degree of experiential freedom, moral freedom, is manifested in the steadfast moral behavior of a mature character. Now, God makes His eternal decisions based on the fullest knowledge and assessment of all possibilities and perspectives, and with His absolute power, He carries them out exactly as He conceived them. Therefore, there can be no new perspective or event that He has not considered since eternity, and which could therefore prompt Him to revise His decisions; nor can any external difficulty or obstacle arise, which would induce Him to try to realize His plans in a different way. God's intentions are free; but precisely because they were born out of the fullest freedom, they are unchangeable. The decisions of creatures can be changed, partly because new perspectives may arise, which were not previously considered, partly because obstacles to realization may necessitate the modification of original plans.
2. God's outward works change. Not only does the world, maintained and governed by God, continually change in big and small ways, but God intervenes in the world's course through miracles, and what's more significant: He created the world in time, the second divine person became flesh in time. Therefore, if God continually creates new works in time, He does something He has not done before; that is, He changes.
Solution. Three aspects can be distinguished in God's outward activity:
A) The decision regarding outward activity. As an immanent fact of God, it is eternal and unchangeable.
B) The change; this takes place in God's works, it does not affect God Himself. With the creation of the world, with the incarnation of the second divine person, God Himself does not change; nothing new happens to Him; because this aspect: "in time" the world should be created etc. was also included in His eternal unchangeable decision; only the creature enters into a new relationship with Him, just as the Sun does not go through a change because it makes winter or summer on Earth.
C) The creation of the changing work, that is, the divine activity that carries out the eternal and unchangeable divine order relating to change. This activity, viewed from the side of God, is identical with God's essence and does not represent a change in God, but only in the result of divine activity. When a doctor not only prescribes medication for a patient but also specifies the time to take it, this provision is the cause of a change that occurs at a specific time; but when it occurs, it does not cause a change in the prescriber; and if the doctor's will were absolutely effective, the patient's time-bound medication intake would occur without the help of any foreign factor, simply as a result of that medical order. That is, the result appearing in time does not necessarily mean a change in the cause. The divine provisions containing changes, however, contain the change only as an intention, as a thought; even in humans, thoughts relating to change do not represent the same type of change for the thinker: if I decide to run, I am not physically running yet. In any case, it is not easy to imagine how the unchanging God creates changes; because our perception is stuck in the world of changes. But there is no logical stumble in the concept. Indeed, if we consider how difficult it is to conceptually process the concept of change, it is logically easier to conceive of God's immutability than the changeability of the creature. That's why the Eleatics and Plato considered being itself to be unchangeable, just like the thinkers of Vedanta.
3. In governing the world, God often adapts to the changing behavior of creatures: He hears the cry of the needy, gets angry at the sinner, is appeased against the penitent. So, He changes.
Solution. It's true, and indeed a matter of faith, that God behaves this way. However, these significant practical truths cannot be interpreted in a way that contradicts the equally fundamental, dogmatic assertion of God's unchangeability. Nor is it necessary, because God does not make and execute decrees on the course of the world in the manner of human beings. He does not first set certain goals and then search and select suitable means; He does not first devise the abstract universal law, and then tailor and apply it to specific cases. Instead, He relates and assigns all events to each other with one overview and decision, providing them with the appropriate levels of value, bringing every path and end, every goal and means, every individual being and individual case, and every general law into perfect harmony. No new element can then arise that was not already considered, which would subsequently require the course of the world to be supplemented or corrected. In this immutable eternal divine decree, every human need and every human prayer were taken into account, and the course of the world is aligned with it; every individual sin was known, and every aspect of the moral order has been adjusted accordingly: the merits and punishments, praises and reprimands, salvations and condemnations. Therefore, prayer, sin or repentance, justification or damnation does not change God, but the creature's relationship to God, in the words of St. Augustine: God "changes if you change"; "the same light is painful to the weak eye, pleasant to the strong." (August. Serm. 22, 6; cf. Trinit. V 16, 17; XIII 11, 15; in Jn 110, 6; Origen De orat. 3–15; Ambr. Noe et arca 4, 9; 45. § 3.)
4. If God is completely immutable, and looks down on the course of the world like some harsh formula or law, then the immediacy and intimacy of religious life freezes before His Medusa-like face. The harsh law and logical formula are deaf to pleas, unyielding to entreaty, indifferent to pain and misery, unresponsive to loyalty, trust, and sacrifice.
Solution. God is not a senseless harsh law, as Hegel's pantheism teaches, nor is He a Shylock who rigidly represents the letter of the law with merciless one-sidedness. Although He is entirely true and holy, meaning He is utterly devoid of caprice, irrationality, whim, or bias (there is no "irrational" or "non-putarem" in God, see Lk 20:15), He still stands as a Creator opposite each of His creatures, each of their existential moments. He created everything with the utmost care, wisdom, and gentleness; He is incomparably closer to each of His creatures than any two creatures are to each other, and therefore He has the most profound love and interest for all their manifestations, including their religious aspects. As an absolute personal being, He takes everything into account in its proper place and for its own value. The fact that He overlooks the entire order of existence does not diminish the strength of His devoted interest and sacred stance against any aspect of existence. Just because He sees the repentance of the sinner as well and incorporates it into His world plan, sin is no less abhorrent to Him; just because He has established the whole course of the world with all its aspects, the righteousness of the righteous and their plea do not become of lesser value to Him. It may happen to people that, due to their constraints, they do harm or injury despite their best intentions by handling a certain aspect one-sidedly (e.g., parents' monkey-love, a clumsy friend's desire to help at all costs); God, because He thinks about everything and everyone, judges man best in individual cases.
Indeed, God's immutability provides new and irreplaceable impetus to religious life. God's immutability is most directly manifested to man in the reliability of His promises and the immutable sanctity of His holy will, the moral law; thus, it is the root and foundation of trust in Him. True, God is not as malleable as humans, He does not adapt to the tastes and moods of people at any given time, and He is not willing to measure with the measures of humans. This is often unpleasant for humans, who, in their stubbornness, whimsicality, and weakness of principles, would inevitably like God to be less holy, to act according to less universal perspectives, and to become biased (see the vine-growers and the prodigal son's brother). But precisely because God is in no way similar to humans, the person leading a serious religious life is most effectively called upon to adapt to God in everything. Our only refuge against the stubbornness of our own nature and the transience of life is the eternal Silent Ocean of divine immutability, where all the noise of passions, party fights, and hustles fade away, where the tossing soul finds its peace. "And the world passeth away, and the lust thereof: but he that doeth the will of God abideth forever." (1 Jn 2,17; cf. 4,16.)
It is also dogma that God is eternal in absolute sense. This is a tenet of faith according to the teachings of the Nicene Creed, the Athanasian Creed, the Fourth Lateran Council, and the First Vatican Council, against all those who denied God's immutability and thus cast doubt on His eternity.
Divine eternity is God's perfection in relation to time, and it negates the following: that the divine existence has an end, a beginning, or a sequence; it affirms: God is the creator of time; it increases: whatever positive content is in time, it is infinitely present in God. Time is the real possibility of real connection between causes and effects; in God, who is the creator of time and eternal, timeless existence is not emptiness, but the fullness of activity, as Boethius's classic definition says: eternity is the complete and perfect possession of endless life (interminabilis vitae tota simul et perfecta possessio). And in this sense, God is eternal.
The Scriptures often denote a very long duration with the term "eternity" (עוֹלָם, αἰῶν = ἀεὶ ὂν, ἀίδιον), mainly infinity (e.g., Gen 17:8, Lev 3:17, Ps 5,12. In this sense, the Creed says: "I believe… in eternal life."), and that's why it often attributes it to creatures, especially spirits. (Mt 25:46, Lk 1:3 etc.) However, it calls God eternal in the above-defined sense, and Him alone; not formally, but in terms of content.
The Scripture denies the elements of time about Him: the beginning, the end, the succession, and declares Him to exist before all time: "Before the mountains were brought forth, or ever thou hadst formed the earth and the world, from everlasting to everlasting thou art God." (Ps 90,2; cf. 2,7, 102,27.) "Verily, verily, I say unto you, before Abraham was, I am." (Jn 8,58.) "I the Lord, the first, and with the last; I am he." (Is 41,4; cf. Gen 1, Ps 93, 102,26–28 Deut 32,40 Dan 7,99 [ʿatīq yōmīn, antiquus dierum, the ancient of days], Rev 1,4–18.)
God and time are not commensurate quantities: "But, beloved, be not ignorant of this one thing, that one day is with the Lord as a thousand years, and a thousand years as one day." (2 Pet 3:8; cf. Heb 1:10, Gen 1:14–19, Deut 33:26, Job 36:26, Ps 74:16, 90:4, 119:89–91, Is 43:3, 48:12, Jer 10:10, 1 Tim 1:17, Rev 4:8–11, 10:6.)
The Church Fathers, already against the pagans, emphasize and regularly discuss divine eternity, especially frequently and wittily by St. Augustine (Tatian. Graec. 4; Athenag. Legat. 4 10; Iren. III 8, 3; Tertul. Marc. I 8; III 28; Nazianz. Or. 38, 7; 45, 3; August. Conf. XI; Ver. relig. 49; in Ps 101: 2, 10 et al.).
Reason also sees that
a) eternity is the direct consequence of immutability. Time is indeed the measure of change based on succession (numerus motus secundum prius et posterius); there is no change in God, so there can be no time either.
b) It is also a consequence of self-existence: self-existence excludes in God the conjunction or succession of potentiality and actuality. However, time only exists with these: the present is potential compared to the past, the future compared to the present. Therefore, God is above temporality (Thom I 10; Gent. I 15 III 68.).
Questions.
The relationship of divine eternity to temporal entities. – God, by virtue of His eternity, is outside and above all time, but as its author, He is present at every moment of time; there is no moment in the flow of time, neither past nor present nor future, in which God does not exist simultaneously; in every actual or thought time, we must say: God is now. Some theologians (like Halens. Summa I 12, 1, 1.) call this God's always-existence (sempiternity) and rightly compare it with ubiquity (omnipresence). Thus, the eternity of God equals each moment of time and the entire timeline, and coexists with it; not like a long line is parallel to a shorter line, but like the center of a circle is with every single point and arc of the circumference (Anselm. Monol. 18; Thom Gent. I 66; Less. Perf. IV 4.). However, this relationship should not be understood as if a part of the timeline, or even the entire timeline, would correspond to a shorter or longer duration in divine eternity; there is no duration in God; eternity is not an infinite sum of durations, as Aureolus thought; time, as the projection of change, cannot be asserted about God in any form.
The coexistence of temporal things with divine eternity. – Temporal things, when they actually exist, are simultaneous with divine eternity. For God is present at every single moment and duration of time; therefore, every single temporal thing is also present before God at every moment of its existence and throughout its duration; and since the eternity of God does not allow time gaps, temporal things are present with the entire divine eternity throughout the duration of their existence; of course, not as commensurate quantities, not like a mayfly or a fly spends a period of time with a longer-lived human, but only as a creation, as a work that essentially and intimately depends on its creator, its thought and sustaining activity. Can it also be said that things are present not only during their actual existence but also before and after their existence with God's eternity, which has no past or future, but only an eternal present («nunc aeternitatis»), which extends over every created moment and duration of time with its power? Thomas Aquinas answers yes (Thom 1 dist. 19, 2, 2 ad 1.). Other theologians, however, see this as endangering both the temporality of creatures and the absolute simplicity of eternity, which excludes even the concept of time intervals.