In theology, the doctrine of divine simplicity says that God is without parts. The general idea of divine simplicity can be stated in this way: 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 God's being, not qualities that make up that being, nor abstract entities inhering in God as in a substance. Varieties of the doctrine may be found in Jewish, Christian, and Muslim philosophical theologians, especially during the height of scholasticism, though the doctrine's origins may be traced back to ancient Greek thought, finding apotheosis in Plotinus' Enneads as the Simplex.
In Christian thought 
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In Christian theism (to be accurate "Classical theism"), God is simple, not composite, not made up of thing upon thing. In other words, the characteristics of God are not parts of God that together make up God. Because God is simple, God is those characteristics; for example, God does not have goodness, but simply is goodness. For typical Christian theologians, divine simplicity does not entail that the attributes of God are indistinguishable to thought. It is no contradiction of the doctrine to say, for example, that God is both just and merciful. Thomas Aquinas, for instance, in whose system of thought the idea of divine simplicity is central, wrote in Summa Theologica that because God is infinitely simple, God can only appear to the finite mind as infinitely complex.
Theologians holding the doctrine of simplicity tend to distinguish various modes of the simple being of God by negating any notion of composition from the meaning of terms used to describe it. Thus, in quantitative or spatial terms, God is simple as opposed to being made up of pieces, present in entirety everywhere, if in fact 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.
Furthermore, according to some, if as creatures our concepts are all drawn from the creation, it follows from this and divine simplicity that God's attributes can only be spoken of by analogy — since it is not true of any created thing that its properties are identical to its being. Consequently, when Christian Scripture is interpreted according to the guide of divine simplicity, when it says that God is good for example, it should be taken to speak of a likeness to goodness as found in humanity and referred to in human speech. Since God's essence is inexpressible; this likeness is nevertheless truly comparable to God who simply is goodness, because humanity is a complex being composed by God "in the image and likeness of God". The doctrine aids, then, in interpreting the Scriptures so as to avoid paradox—as when Scripture says, for example, that the creation is "very good", and also that "none is good but God alone"—since only God is goodness, while nevertheless humanity is created in the likeness of goodness (and the likeness is necessarily imperfect in humanity, unless that person is also God). This doctrine also helps keep trinitarianism from drifting 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 properties of God such as goodness etc., then God is a property; and a property is not a person. Plantinga concludes that divine simplicity does not do justice to the personal nature of the Christian God.
In Jewish thought 
In Jewish philosophy and in Jewish mysticism Divine Simplicity is addressed via discussion of the attributes (תארים) of God, particularly by Jewish philosophers within the Muslim sphere of influence such as Saadia Gaon, Bahya ibn Paquda, Yehuda Halevi, and Maimonides, as well by Raabad III in Provence.
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.
- On the one hand, God is absolutely simple, containing no element of form or structure, as above.
- On the other hand, it is understood that God's essence contains every possible element of perfection: "The First Foundation is to believe in the existence of the Creator, blessed be He. This means that there exists a Being that is perfect (complete) in all ways and He is the cause of all else that exists." (Maimonides 13 principles of faith, First Principle).
|“||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 God] 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.
- See also: Tzimtzum; Negative theology; Jewish principles of faith; Free will In Jewish thought; Kuzari
See also 
- Bussanich John, Plotinus's metaphysics of the One in The Cambridge Companion to Plotinus, ed. Lloyd P.Gerson, p.42, 1996, Cambridge University Press, UK. For instances, see Plotinus, Second Ennead, Fourth Tractate, Section 8 (Stephen MacKenna's translation, Sacred Texts)
- Plotinus, Fifth Ennead, Fourth Tractate, Section 1 (MacKenna's translation, Sacred Texts)
- Plotinus, Second Ennead, Ninth Tractate, Section 1 (MacKenna's translation, Sacred Texts).
- Plantinga, Alvin. "Does God Have a Nature?" in Plantinga, Alvin, and James F. Sennett. 1998. The analytic theist: an Alvin Plantinga reader. Grand Rapids, Mich: W.B. Eerdmans Pub. Co., 228. ISBN 0-8028-4229-1 ISBN 978-0-8028-4229-9
- 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. K. Scott Oliphint, Reasons [for faith]: philosophy in the service of theology (Phillipsburg, N.J.: Presbyterian & Reformed, 2006. ISBN 0-87552-645-4 ISBN 978-0-87552-645-4
- Burell, David. Aquinas: God and Action. London; Routledge & Kegan Paul, 1979.
- Burell, David. Knowing the Unknowable God: Ibn-Sina, Maimonides, Aquinas.. Notre Dame: Notre Dame University Press, 1986.
- Leftow, Brian. "Is God and Abstract Object?". Nous. 1990.
- Maimonides, Moses. The Guide of the Perplexed, trans. M Friedländer. New York: Dover, 1956.
- Plantinga, Alvin. Does God Have a Nature? Milwaukee, WI: Marquette University Press, 1980.
- Plato. Parmenides. Many editions.
- Plotinus. Enneads V, 4, 1; VI, 8, 17; VI, 9, 9-10. . Many editions.
- Pseudo-Dionysius. The Divine Names in Pseudo-Dionysius: The Complete Works, trans. Colm Luibheid. New York: Paulist Press, 1987.
- Stump, Eleonore and Kretzmann, Norman. “Absolute Simplicity”. Faith and Philosophy. 1985.
- Thomas Aquinas. On Being and Essence (De Esse et Essentia), 2nd ed., trans. Armand Maurer, CSB. Toronto: Pontifical Institute of Medieval Studies, 1968.
- Thomas Aquinas. Summa Theologica I, Q. 3, A. 3 "On the Simplicity of God". Many editions.
- Wolterstorff, Nicholas. "Divine Simplicity". Philosophical Perspectives 5: Philosophy of Religion. Atascadero, Calif.: Ridgeview Publishing, 1991, 531-52.
- Christian material
- On Three Problems of Divine Simplicity, Alexander R. Pruss, Georgetown University
- St. Thomas Aquinas: The Doctrine of Divine Simplicity, Michael Sudduth, Analytic Philosophy of Religion
- Jewish material
- "Paradoxes", in "The Aryeh Kaplan Reader", Aryeh Kaplan, Artscroll 1983, ISBN 0-89906-174-5
- "Innerspace", Aryeh Kaplan, Moznaim Pub. Corp. 1990, ISBN 0-940118-56-4
- Understanding God, Ch2. in "The Handbook of Jewish Thought", Aryeh Kaplan, Moznaim 1979, ISBN 0-940118-49-1
- Shaar HaYichud - The Gate of Unity, Dovber Schneuri - A detailed explanation of the paradox of divine simplicity.
- Chovot ha-Levavot 1:8, Bahya ibn Paquda - Online class, Yaakov Feldman