In theology, the doctrine of divine simplicity says that God is without parts. The general idea of divine simplicity can be stated as, that the being of God is identical to the attributes of God. In other words, such characteristics as omnipresence, goodness, truth, eternity, etc. are identical to his/her/its being, not qualities that make up his/her/its being.
When theology follows this doctrine, various modes of simplicity are distinguished by subtraction of various kinds of composition from the meaning of terms used to describe God. Thus, in quantitative or spatial terms, God is simple as opposed to being made up of pieces: he is present in his entirety everywhere that he is present, if he is present anywhere. In terms of essences, God is simple as opposed to being made up of form and matter, or body and soul, or mind and act, and so on: if distinctions are made when speaking of God's attributes, they are distinctions of the "modes" of God's being, rather than real or essential divisions. And so, in terms of subjects and accidents, as in the phrase "goodness of God", divine simplicity allows that there is a conceptual distinction between the person of God and the personal attribute of goodness, but the doctrine disallows that God's identity or "character" is dependent upon goodness, and at the same time the doctrine dictates that it is impossible to consider the goodness in which God participates separately from the goodness which God is in Himself.
Furthermore, it follows from this doctrine that God's attributes can only be spoken of by analogy - since it is not true of any created thing that its properties are (is?) its being. Consequently, when Christian Scripture is interpreted according to the guide of divine simplicity, when it is said that God is good for example, it is nearer to the actual case that the Scriptures speak of a likeness to goodness, in man and in human speech, since God's essence is inexpressible; this likeness is nevertheless truly comparable to God who is simply goodness, because man is constructed and composed by God "in the image and likeness of God". The doctrine assists then for the interpretation of the Scriptures without paradox, when it is said for example that the creation is "very good", and also that "none is good but God alone" - since only God is good in himself, while nevertheless man is created in the likeness of goodness (and the likeness is necessarily imperfect in man, unless that man is also God). This doctrine also helps keep trinitarianism from drifting or morphing into tritheism, which is the belief in three different gods: the persons of God are not parts or essential differences, but are rather the way in which the one God exists personally.
The doctrine has been criticized by some Christian theologians, including Alvin Plantinga, who in his essay Does God Have a Nature? calls it "a dark saying indeed Plantinga's criticism is based on his interpretation of Aquinas's discussion of it, from which he concludes that if God is identical with his properties, then God himself is a property; and a property is not a Person: and therefore, divine simplicity does not describe the Christian God, according to Plantinga. K. Scott Oliphint in turn criticizes Plantinga for overlooking the better expressions of divine simplicity, saying that his argument is "admirable" as a critique of the impersonalism of speculative philosophy, but "not so valuable" as a criticism of the Christian formulation based on verbal revelation.
John Cobb and David Ray Griffin argue against this idea of divine simplicity. They take a look at the Perfect Being Theology, where God is defined as being impassible. Therefore, if God is unaffected by human actions, then God is not sympathetic. Therefore God would not be loving. However, God is considered to be loving, which causes God to not be a simple being.
Some identify Divine simplicity as a corollary of Divine Creation: "In the beginning God created the heaven and the earth" (Genesis 1:1). God, as creator is by definition separate from the universe and thus free of any property (and hence an absolute unity); see Negative theology.
For others, conversely, the axiom of Divine Unity (see Shema Yisrael) informs the understanding of Divine Simplicity. Bahya ibn Paquda (Duties of the Heart 1:8) points out that God's Oneness is "true oneness" (האחד האמת) as opposed to merely "circumstantial oneness" (האחד המקרי). He develops this idea to show that an entity which is truly one must be free of properties and thus indescribable - and unlike anything else. (Additionally such an entity would be absolutely unsubject to change, as well as utterly independent and the root of everything.)
The implication - of either approach - is so strong that the two concepts are often presented as synonymous: "God is not two or more entities, but a single entity of a oneness even more single and unique than any single thing in creation… He cannot be sub-divided into different parts — therefore, it is impossible for Him to be anything other than one. It is a positive commandment to know this, for it is written (Deuteronomy 6:4) '…the Lord is our God, the Lord is one'." (Maimonides, Mishneh Torah, Mada 1:7)
Despite its apparent simplicity, this concept is recognised as raising many difficulties. In particular, insofar as God's simplicity does not allow for any structure — even conceptually — Divine simplicity appears to entail the following dichotomy.
God’s existence is absolutely simple, without combinations or additions of any kind. All perfections are found in Him in a perfectly simple manner. However, God does not entail separate domains — even though in truth there exist in God qualities which, within us, are separate… Indeed the true nature of His essence is that it is a single attribute, (yet) one that intrinsically encompasses everything that could be considered perfection. All perfection therefore exists in God, not as something added on to His existence, but as an integral part of His intrinsic identity… This is a concept that is very far from our ability to grasp and imagine…
The Kabbalists address this paradox by explaining that “God created a spiritual dimension… [through which He] interacts with the Universe... It is this dimension which makes it possible for us to speak of God’s multifaceted relationship to the universe without violating the basic principle of His unity and simplicity” (Aryeh Kaplan, Innerspace). The Kabbalistic approach is explained in various Chassidic writings; see for example, Shaar Hayichud, below, for a detailed discussion.