Thomas Aquinas and the Arabic Philosophers: A Brief Look

“Say, ‘He is Allah, the One;

Allah, the Eternal, Absolute;

He begets not, and neither is He begotten;

And there is nothing that can be compared to Him.”

Qur’an 112:1-4

“Hear, O Israel, the Lord our God is one Lord.”

Deuteronomy 6:4


The Arabic philosophers of the middle ages took various positions in affirming the divine simplicity and unchangeableness of God when seeking to understand His relation to all other existing things.

All sought to defend the divine simplicity, but in various and often mutually exclusive ways.  It would be up to Thomas Aquinas, familiar with their efforts at a unification of faith and reason, to reconcile the unchangeable God and His “relation” to creation.


“God” according to Plotinus, the unofficial founder of Neoplatonism, is the One, and is beyond being. Being itself, for him, has a finite character, as it applies to that which we experience, and we only experience things that are finite and changing.  We can see here a bit of Aristotelian epistemological realism, but with a heavy bias towards the metaphysics of Plato.  What else should we expect from Plotinus?

God, who is unchangeable, is necessarily “beyond” being, although  this is certainly not to say that he does no exist.  It will probably always be somewhat unclear exactly what this means, but the point seems to be to keep God from being “part of our world.”

This point itself will be shown to be of great importance to the Islamic and Christian beliefs about God, although to say God is beyond being or other than being will not of itself always be the reasoned answer.


Early Islamic thought on God’s immutablility is highly influenced by Neoplatonic thought, as we might expect.  If we start with al-Kindi, we see, in On First Philosophy, that a major theme of his metaphysics is on wahda, or oneness, an attribute that can only be truly said of God. Any other thing, such as “one person,” is really one and many, it is spread out, it has parts, etc.

Al-Kindi sees God as active in the role of creation, however.  In this, he differs from many of the later Neoplatonic Arabic philosophers, who adhere more closely to the pure emanationist scheme of classical Neoplatonism.

Al-Farabi, who followed soon after al-Kindi, is a perfect example of such thought.  His cosmology and metaphysics tie together in a system of hierarchical emanationism.  This certainly still has an Aristotelian flavor, as he sees God as the prime mover, moving the spheres of the cosmos (through passion for the One), which in turn are causes of movement in the terrestrial sphere.

One still wonders, with an emanationist natural theology, how the “multiplication of gears starts the clock,” or rather, how merely multiplying the levels between us and God removes God from an relation to us.


When we now turn to Avicenna, we will see a more strict adherence to Aristotelian thought.

Avicenna was much more in line with Aristotelian metaphysics , and he deeply engaged his mind in trying to show that God was absolutely unchangeable.  This led him to a denial of creation, for this would be an act of God that would change Him in some way, or be a change in Him.  The eternity of the world, as understood by Aristotle, was also key in his thought.

Necessary being was an important doctrine of his, as was the beginnings of a distinction between essence and existence.  These were highly influential on how he understood God, and so we will examine a few of his statements on these two matters at present.

“From what we have asserted it follows necessarily that that whose existence is necessary is not relative, not changeable, not multiple, not sharing in respect to the existence which is peculiar to it.” (Healing, I, 6) One however, must wonder at his need for a “cause” of that which does not exist. “Furthermore, everything whose existence is possible has, when it is considered in respect to itself, both its existence and its non-existence from a cause.” We will see that “necessary existence, having no share in reference to that which is peculiar to it” can certainly be agreed to, although in a somewhat different way, when we come to St. Thomas Aquinas.

As for essence and existence, this will be an important distinction for St. Thomas as well.  There is much debate on exactly how Avicenna understood these terms. “Existence, according to Avicenna, is superadded to essence or, in alternate language, it is its accident,” says an article in Philosophy in the Middle Ages. Our Cambridge Companion would say this claim is not certain.


We will here look at some questions in purely philosophical terms as St. Thomas examined them.  Important for our inquiry will be Thomas’ work Quaestiones Disputatae de Potentia Dei, or Disputed Question on the Power of God.  We will refer here primarily to Question 7 on the Simplicity of the Divine essence, especially articles VIII-XI.  Below are some important quotes from this section as regards God’s immutabilty in the light of his relation to contingent being:

Article VIII: Is There Any Relation Between God and the Creature?


  1. The Philosopher(Aristotle) proves (Phys. v) that there can be no movement in relation: since without any change in the thing that is related to another, the relation can cease for the sole reason that this other is changed. Thus it is clear with regard to action that there is no movement in respect of action except metaphorically and improperly speaking, just as we say that one who passes from inaction into action is changed: and this, would not be the case if relation or action signified something abiding in the subject. Hence it is evident that it is not incompatible with a thing’s simplicity to have many relations towards other things: indeed the more simple a thing is the greater the number of its concomitant relations: since its power is so much the less limited and consequently its causality so much the more extended.
  2. Although God is not in the same genus as the creature as a thing contained in a genus, he is nevertheless in every genus as the principle of the genus: and for this reason there can be relation between the creature and God as between effect and principle.
  3. From whichever extreme a change is wrought in that which caused the relationship, the relationship between them ceases. Accordingly from the fact that a change is wrought in the creature, a relation begins ‘to be attributed to God. Hence he cannot be said to become except metaphorically; inasmuch as he is like a thing that becomes, through something new that is said about him: thus we say (Ps. 89): Lord, thou art become our refuge.
  4. God’s existence does not depend on creatures as neither does the builder’s existence depend on the house: wherefore just as it is accidental to the builder that the house exists, so is it accidental to God that the creature exists. For we say that anything without which a thing can exist is accidental to it.

Article VIII dealt with the question “Is There Any Relation Between God and the Creature?” Article X, however, will deal with the question “Is God Really Related to the Creature So That this Relation Be Something in God?”  We will see that, although it may appear to be a similar question to that of Article VIII, it is actually quite different.  The answers of Thomas will demonstrate such:

  1. As the knowable thing is the measure of knowledge, so is God the measure of all things, as the Commentator says (Metaph. x). Now the knowable thing is not referred to knowledge by a real relation existing in it, but rather by the relation of knowledge to it, as the Philosopher says (Metaph. v). Therefore seemingly neither is God related to the creature by a real relation in him.
  2. “Likeness is not reciprocal between cause and effect, for an effect is said to be like its cause and not vice versa.” (Quoting Pseudo-Dionysius, Div. Nom. ix) Now the same would seem to apply to other relations as to that of likeness. Therefore, seemingly neither is there reciprocity in the relations between God and the creature, and we cannot argue that because the creature is really related to God, therefore is God really related to the creature.

This last response is the key to Thomas solution.  As opposed to what Avicenna would say in regards to creation, Thomas could go on from here to say that the creature, including its contingency and its coming to be, impose no change on God, even though there is an absolutely real relationship from the creature to God.


A relationship from creature to God does not, in other words, impose a relationship on God to the creature.  We are forced to say that the relationship “half” has a corresponding relationship “double.” What we are not forced to say is that a relationship of and in creation to God, even as coming to be from God, has a counter in God Himself.


The Arabic philosophers of the middle ages took various positions in affirming the divine simplicity and unchangeableness of God when seeking to understand His relation to all other existing things:

Allah is one, and we have seen that, whatever the philosophical presuppositions,  nothing that gave way to a “changing god” would be tolerated.

All sought to defend the divine simplicity, but in various and often mutually exclusive ways:

The Arabic philosophers used various metaphysical theories to try and explain reality, whether it be that of Neoplatonism, a strict Aristotelianism, or even an abandonment of the idea that  any philosophy itself could accurately say anything of truth about God.

It would be up to Thomas Aquinas, familiar with their efforts at a unification of faith and reason, to reconcile the unchangeable God and His “relation” to creation:

Thomas Aquinas, with his doctrine of analogy and his understanding of God through both philosophical insight and Biblical revelation, especially that of Exodus 3:14, could come to the metaphysical and logical conclusion that God could be shown to be true            creator and true unchanging existence Himself.

He Who is, Is.

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