SECTION 2. -- The Simplicity of God.

Thesis VIII. -- God's Being is physically and metaphysically simple.

61. What is one is undivided in so far as it is one; what is simple, is not only undivided but indivisible. Oneness does not exclude composition, although it excludes division; with simplicity all composition is incompatible. Every man is one natural being, but he is not one simple being, because he consists of two substantial principles, body and soul, united with one another. Man therefore is composed of substantial parts; in him there is substantial composition. If we consider the immaterial soul of man alone, we have a being not composed of substantial parts, and therefore rightly called a simple substance. Nevertheless, even the soul is not exempt from all composition. It is liable to accidental composition. For it is changeable in regard to its thoughts and volitions, so that we can distinguish these and it as component parts of a whole. Both these kinds of composition are found in existing things, and we call them real or physical composition. In God neither of them exists, consequently He is physically simple in the strictest sense.

The proof of the physical simplicity of God rests upon His self-existence. Whatever is substantially compounded, depends in its essential constitution upon the union of parts, each of which differs from the compound substance. But since the self-existent owes nothing to what is different from itself, its essential constitution cannot depend upon the union of parts different from itself. Therefore God, being self-existent, cannot be substantially compounded. Nor is accidental composition conceivable in the Divine Being. How could it be? An accident is a perfection or modification added to the nature of a substance. But to the nature of the Divine Substance no perfection or modification can be added. Any addition made could not be the addition of anything self-existent, because what falls under the conception of self-existence belongs to the Divine Nature itself. Nor, again, could it be the addition of anything not self-existent: because what is not self-existent cannot be found in the Divine Nature.

The same follows from the infinity of God which, as we shall see, is a corollary of God's self-existence and unity. This infinity supposed, we argue thus: What is infinitely perfect can receive no addition. But every accident is an addition to the substance in which it inheres. Therefore a being infinitely perfect, as God's Being really is, can receive no accident.

62. Moreover God is not only physically simple, but also metaphysically. As physical simplicity excludes physical composition, so metaphysical simplicity excludes metaphysical composition. The difference between physical (real) and metaphysical (virtual) composition may be thus expressed: Physical composition means union of diverse realities completing one another to constitute one really existing being, as for instance, man is a physical compound of body and soul; metaphysical composition means union of diverse concepts referring to the same real being in such a way that none of them by itself signifies either explicitly or even implicitly the whole reality signified by their combination; man, for instance, is a metaphysical compound of animal and rational. This metaphysical composition belongs to all creatures, even to such as are physically simple. The reason for this assertion is obvious enough. That which is signified by the definition of a created thing, its essence as we call it, depends for its existence, not upon itself, but upon its creating cause. Without the influx of the creating power of God the creature is nothing but an objective idea of the Divine Mind, something known only as capable of existing under the condition that God wills its existence. In other words, the essence of every creature is in itself a mere possibility; not a real, but a conditional existence. In conceiving its essence, or the contents of its definition, we thereby neither express nor imply its existence. Consequently the objective concept of the real existence of a creature is metaphysically compounded of the two concepts of its essence and existence.^{6} That this first kind of metaphysical composition cannot be predicated of God is evident; for its only foundation is the contingency of created being; therefore it must be alien to the Divine Nature, which exists with absolute necessity.

63. Another sort of metaphysical composition in creatures is that contained in the objective concept of their specific nature. The species man or rational animal includes what is meant by the two concepts animal and rational. As the former is equally applicable to irrational beasts and to men, it evidently neither expresses nor implies the meaning of the concept rational. Therefore we say that human nature is metaphysically composed of the genus animal and the specific difference rational. Now this sort of metaphysical composition is incompatible with the Divine Nature; because God cannot be included in any genus of beings. Beings can be classed as one genus, only so far as under some one aspect their essences are perfectly similar, occupying in this respect a perfectly equal position in the scale of beings. But God cannot be perfectly similar to any order of beings diverse from Himself under any aspect whatsoever; because all other beings are dependent upon Him; they are, as it were, an outflow of His unchangeable simple self-existence. His justice cannot be perfectly similar to any sort of created justice, nor His mercy to any mercy belonging to any of His creatures. Borrowing a beautiful, although necessarily inadequate illustration from the Angelic Doctor,^{7} we may say: As the sun by his light and heat is the unapproachable principle of millions of forms of life and growth, so God by His wisdom and power is the unapproachable principle of all kinds of beings, surpassing in His simplicity the manifold perfections of all and each of them by an infinite distance. It is this which Mr. Herbert Spencer has in view when he rightly maintains that those who admit a first self-existing unconditional Being must admit that this Being cannot be classified. "Between the creating and the created," he says,^{8} "there must be a distinction transcending any of the distinctions existing between different divisions of the created. . . . The infinite cannot be grouped along with something that is finite; since, in being so grouped, it must be regarded as not-infinite. It is impossible to put the absolute in the same category with anything relative, so long as the absolute is defined as that of which no necessary relation can be predicated. . . . There cannot be more than one First Cause. . . . The unconditioned therefore as classable neither with any form of the conditioned nor with any other unconditioned cannot be classed at all." So far so good. But when the same author goes on to say of the unconditioned First Cause: "To admit that it cannot be known as of such or such kind, is to admit that it is unknowable," he certainly is wrong. It is true, from the impossibility of classifying God with any creatures, it follows that no creature can know Him adequately as He is knowable and known by Himself; that no creature can comprehend Him. But our inability to comprehend God does not imply that we cannot predicate of God whatever real perfection there is in creatures. Later on we shall give reasons to show that we have a real and true knowledge of God, however utterly inadequate it may be.

64. For the present we may add that not only the metaphysical composition mentioned above, but any conceivable sort of metaphysical compositions are all inapplicable to God. The general reason for this may be stated thus: Concepts which in their application to objective reality are absolutely inseparable, so that none of them can have a real foundation different from the real foundation of the rest, cannot be metaphysically compounded. For though none expresses what is expressed by the others, yet each of them implies all the rest. But the concepts which we form of the Divine attributes are in their application to objective reality absolutely inseparable. Each of the Divine attributes in its objective reality coincides with the one self-existing Divine substance, which we have proved to be a simple unchangeable essence. Consequently none of the Divine attributes has any objective foundation except in so far as it is one with the rest; which is evidently the same as to say that the Divine attributes are absolutely inseparable in their application to objective reality. Divine justice, for instance, without Divine mercy is impossible; and so is Divine power without Divine wisdom. Therefore these attributes are not metaphysically compounded, although they must be said to be metaphysically or virtually distinct; the concept of justice does not express what is expressed by the concept of mercy, although it implies the same.^{9}

{6} St. Thomas and the scholastics expressed this briefly by saying that in no created thing are essence and existence the same; and that every created thing is composed of essence and existence, or of potentiality and actuality (potentia and actus).

{7} Sum. Theol. i. q. 4. a. 2. ad 1m.

{8} First Principles, p. 81.

{9} Real distinction does not necessarily mean real composition, nor does virtual distinction necessarily mean virtual composition. For things to be compounded they must first be distinct; but, given the existence of distinct things, it is not necessary that they should be compounded together into a unity. Catholic Theology recognizes a real distinction between the three Divine Persons, because They are, as "substantial" relations within the One Godhead, opposed to one another; but it is not constrained in consequence to admit that the Godhead is really compounded of Them, because it teaches that each Person is not really distinct from, but really identical with, the Essence of the Divinity. Again, Catholic Theology recognizes a virtual distinction between the Divine Essence and each Divine Person, but it does not teach us that the Divine Essence is virtually compounded of the three Persons, because the concept of each Divine Person does not prescind from, but involves the concept of the Divine Essence. These observations show us that the mystery of the Blessed Trinity is opposed neither to the physical nor to the metaphysical simplicity of God.