The Nature of God – Part 1

By: Dr. Norman Geisler; ©2003
Natural theology deals with what can be known about the existence and nature of God by natural reason, apart from any supernatural revelation. According to classical Christian theists, all of the essential metaphysical attributes of God can be known by natural reason. Dr. Geisler explains some of those attributes in this article.

The Nature of God—Part 1

Natural theology deals with what can be known about the existence and nature of God by natural reason, apart from any supernatural revelation. According to classical Christian theists, such as Thomas Aquinas (1225-1274), all of the essential metaphysical attributes of God can be known by natural reason. This includes God’s aseity, simplicity, immutability, eternality, simplicity, unity, infinity, and morality.

Aseity (Self-Existence)

Most classical theists see God’s Aseity or Pure Existence as a key attribute. The early Church Fathers, as well as Augustine (354-430), Anselm (1033- 1109), and Aquinas, continually cite the Bible in support of this position. In defending God’s self-existence (aseity) classical theists such as Aquinas are fond of citing Exodus 3:14 where God identifies himself to Moses as “I Am that I Am.” This they understand to refer to God as Pure Being or Existence.

God is Pure Actuality, with no potentiality in his being whatsoever. Whatever has potenti­ality (potency) needs to be actualized or effected by another. And since God is the ultimate Cause, there is nothing beyond him to actualize any potential (i.e., ability) he may have. Nor can God actualize his own potential to exist, since this would mean he caused his own existence. But a self-caused being is impossible, since it cannot create itself. Something has to exist before it can do anything. Even God cannot lift himself into being by his own ontological bootstraps. Thus, God must be Pure Actuality in his Being.

Of course, God has the potential to create other things. But he cannot bring himself into being. He always was. And while God has the potential to do other things, he cannot be anything other than what he is. He has the power to create other things (active potency), but he does not have the power (passive potency) to exist in any other way than he does, namely, as an infinite, eternal, necessary, and simple Being.

God’s aseity means that he is Being; everything else merely has being. God is Pure Actuality; all other things have both actuality and potentiality. Thus, God cannot not exist. All creatures can be nonexistent. That is, they have the potentiality for nonexistence. Only God is a Necessary Being. All other beings are contingent.

Simplicity (Indivisibility)

Since God is not composed in his Being, but is Pure Exist­ence, Pure Actuality with no potentiality; it follows that he is simple and indivisible. A Being that by nature is not composed cannot be decomposed. One that has no parts cannot be torn apart. Hence, God has absolute simplicity with no possibility of being divided. He is literally indivisible.

Likewise, a God of Pure Actuality with no potentiality cannot be divided. For if it were divisible, then it would have to have the potential to be divided. But Pure Actuality has no potentiality in its Being whatsoever. Hence, it must be absolutely simple or indivisible.

God’s indivisibility follows also from his immutability (see below). For if God could be divided, he could change. But God is unchangeable by nature. Thus he cannot be divided. He must be absolutely simple in his nature.

Necessity (Noncontingency)

God is by nature an absolutely necessary Being. That is, he cannot not exist. God is not a may-be but a must-be kind of Being. He is not contingent, since he does not have the possibility not to exist. If he has no potentiality not to exist, then he must exist.

This is not to say that the ontological argument is valid. Aquinas considered and rejected Anselm’s proof for God. If God (i.e.. Pure Actuality) exists, then he must exist necessarily. But one cannot simply define him into existence. Aquinas offered his famous cosmological arguments for God’s existence (Summa Theologica, 1.2.3). And once we know, from rea­son and revelation, that God exists, then we can be sure that he must exist necessarily. Such a Being has no potential not to exist.

Immutability (Unchangeability)

In his epic Summa Theologica (1a.9.1), Aquinas offers three basic arguments in favor of God’s unchangeability. The first argument is passed on the fact that a God of Pure Actuality (“I-Am-ness”) has no potentiality. It follows, therefore, that God cannot change (Exod. 3:14). Whatever changes has to have the potential to change. But as pure Actuality, God has no potential, so he cannot change.

The second argument for God’s immutability follows from his simplicity. Everything that changes is composed of what changes and what does not change. God cannot change because an absolutely simple being has no composition. If everything about a being changed, then it would be an entirely new being. In fact, it would not be change but annihi­lation of one thing and a creation of something entirely new. Now if, in every change in a being something remains the same and something does not, then it must be composed of these two elements. So an absolutely simple Being with no composition cannot change.

The third argument for Gods unchangeability argues from his absolute perfection. What­ever changes acquires something new. But God cannot acquire anything new, since he could not be better or more complete. Therefore, God cannot change. If he did, he would not be God for he would have lacked some perfection.

Aquinas also argues that God alone is immutable (Summa Theologica, 1a.9.2). All creatures exist only because of the will of the Creator. His power brought them into exist­ence, and it is his power that keeps them in existence. Therefore, if he withdrew his power they would cease to exist. Whatever can cease to exist is not immutable. Therefore, God alone is immutable; everything else could cease to exist.

Impassability (without Passions)

A long-recognized attribute of God that has recently come under attack is impassability. God is without passions. Passion implies desire for what one does not have. But God, as an absolutely perfect Being, lacks nothing. To lack something he would have to have a potentiality to have it. But God is Pure Actuality with no potentiality whatsoever. Therefore, God is completely and infinitely satisfied in his own perfection.

However, to say that God is impassable in the sense that he has no passions or cravings for fulfillment is not to say that he has no feelings. God feels anger at sin and rejoices in righteousness. But God’s feelings are unchanging. He always, unchangingly, feels the same sense of anger at sin. He never ceases to rejoice in goodness and lightness. Thus, God has no changing passions, but he does have unchanging feelings.

Eternity (Nontemporality)

God is not temporal (Summa Theologica, 1a.10, 1). He is beyond time. Aquinas offers several arguments in support of this conclusion. The first argument goes:

  1. Whatever exists in time can be computed according to its befores and afters.
  2. Changeless being, as God is, has no befores or afters; it is always the same.
  3. Consequently, God must be timeless.

Time is duration characterized by substantial and accidental changes. A substantial change is a change in what something is. Fire changes what a piece of wood is. An acci­dental change is a change in what something has. Growing knowledge is an accidental change in a being. Aquinas sees three levels of being in relation to time and eternity:

  1. God in eternity is Pure Actuality, without essential or accidental change.
  2. Angels and saints who dwell in the spiritual world of heaven live in aeviternity (or aevum).
  3. Human beings, comprising soul and body, form and matter, live in time.

Eternity (God) endures without any potency. Aeviternity (angels) endure with completely actualized potency. Their changes are not essential but accidental. Spiritual beings in aeviternity do not change in their essence, though they do undergo accidental changes. Angels increase in knowledge by divine infusion, and they have changeableness with regard to choice, intelligence, affections and places (ibid., 1a.10.6). But with no substantial changes in aeviternity, angels are immutable in their level of grace and charity. What is true of the angels is also true of the elect in heaven.

Time (humanity) endures with progressive actualized potency.

The second argument for God’s eternity similarly follows from immutability. It begins with the premise that whatever is immutable does not change in the state of its being. Whatever is in time goes through a succession of states. So whatever is immutable is not temporal. This argument stresses another aspect of time; whatever is temporal has successive states, one after the other. God does not, so he is not temporal.

Total immutability necessarily implies eternity (ibid., 1a.10.2). For whatever changes substantially is in time and can be computed according to before and after. Whatever does not change cannot be in time, since it has no different states by which before and after can be computed. It never changes. Whatever does not change is not temporal. Not only is God eternal, but he alone is eternal (ibid., 1a.10.3), for he alone is essentially immutable.

Aquinas distinguishes eternity from endless time (ibid., 1a.10.4). First, whatever is es­sentially whole (eternity) is essentially different from what has parts (time). Eternity is now forever; time includes past, present, and future, now and then. The implication of this is that God’s eternity is not divided; it is all present to him in his eternal now. So it must be essen­tially different from time in successive moments.

Second, endless time is just more an elongation of time. But eternity differs qualitatively. It differs essentially, not merely accidentally. Eternity is an essential, changeless state of being that transcends moment-by-successive-moment reality. Time measures that reality; or rather the stage on which reality plays out.

Third, an eternal being cannot change, whereas time involves change. By change can the measurements of before and after be made. Whatever can be computed according to before and after is not eternal. Endless time can be computed according to before and after. Hence, endless time is not the same as eternity. The eternal is changeless, but what can be computed by its before and after has changed. It follows, then, that the eternal now cannot live in relation to endless befores and afters.

Obviously, Aquinas saw a crucial difference between the “now” of time and the “now” of eternity (ibid.). The now of time is movable. The now of eternity is not movable in any way. The eternal now is unchanging, but the now of time is ever changing. There is only an analogy between time and eternity; they cannot be the same. God’s now has no past or future; time’s now does.

Some have mistakenly concluded that Aquinas did not believe in God’s duration for eternity, because he rejected temporality in God. Aquinas argued that duration occurs as long as actuality exists. But eternity, aeviternity, and time endure in different ways.

It follows, therefore that the essential difference in the quality of the duration in time, aeviternity, and eternity comes from the condition of the actuality. God is Pure Actuality. Angels have received total actuality from God in their created spiritual forms. Human be­ings progressively receive actuality in both spiritual form and material body.

Since God endures without potentiality, he cannot endure progressively. He endures in a much higher way—as Pure Actuality.


Along with eternity is the attribute of immensity (nonspatiality). God is not limited in time, nor is he limited in space. In God’s immanence he fills space, but he is not spatial. Only material things exist in space and time, and God is not material. “God is spirit” (John 4:24). As spiritual, God is not material or spatial. It is part of God’s transcendence that he is beyond both time and space.


Classical theists have offered three reasons for God’s unity (ibid., 1a.11.3). The first argument is from the simplicity of God. An absolutely simple being cannot be more than one, since to be more than one there must be parts, but simple beings have no parts. Absolutely simple beings are not divisible. God is an absolutely simple being. Therefore, God cannot be more than one being.

God’s perfection argues for his unity. If two or more gods existed, they would have to differ. In order to differ, one must have what the other lacks. But an absolutely perfect being cannot lack anything. Therefore, there can only be one absolutely perfect being. God’s unity also can be inferred from the unity of the world. The world is composed of diverse things. Diverse things do not come together unless they are ordered. But the world has an ordered unity. Therefore, there must be one Orderer of the world.

Theists argue that essential unity is better explained by one Orderer than by many orderers. For one is the essential cause of oneness, but many is only the accidental cause of oneness. Therefore, it is reasonable to infer that there is only one cause of the world, not many.

Relatability (to the World)

One criticism of classical theism is that an eternal, unchang­ing God could not relate to a changing world. Aquinas anticipated this objection and treated it extensively.

There are three kinds of relations: One where both terms are ideas; one where both terms are real; and one where one term is real and one is an idea (ibid., 1a.13.7).

Now since creatures are dependent on God but God is not dependent on them, they are related as real to an idea. That is. God knows about the relationship of dependence but he does not have it. When there is a change in the creature there is no change in God. Just as when the man changes his position from one side of the pillar to the other, the pillar does not change; only the man changes in relation to the pillar. So, while the relationship be­tween God and creatures is real, God is in no sense dependent in that relationship.

Aquinas is only denying dependent relationships, not all real ones. God never changes as he relates to the world, but real changes do occur in that relation with the world. The man’s relation to the pillar really changes when he moves, but the pillar does not change.

The real but unchanging relation of God to the world is made even more clear when Aquinas considers how the eternal God relates to a temporal world (ibid., 1a.13.7, ad 2). God condescends to relate to humans as if he shared time with them. He can create a temporal relation that in no way changes him. Eternity can move in time, though time can­not move in eternity. To have a relationship with the temporal world, God does not have to be temporal. It makes no more sense to say God has to be temporal in order to relate to a temporal world than to say he has to be a creature in order to create.

God is really related to creatures as their Creator. But creatures are really related to God only because he is their Creator. They are dependent on that Creator-creature bond; he is not. Therefore, the relation of God to creatures is real and not merely ideal. However, it is a real relationship of dependence on the part of the creatures but not a relation of depen­dence on the part of God (ibid., 1a.13.7, ad 5).

(to be continued)

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