The argument from design also starts from human experience: in this case the perception of order and purpose in the natural world. The argument claims that the universe is strongly analogous, in its order and regularity, to an artifact such as a watch; because the existence of the watch justifies the presumption of a watchmaker, the existence of the universe justifies the presumption of a divine creator of the universe, or God. Despite the powerful criticisms of the Scottish philosopher David Hume (1711–76)—e.g., that the evidence is compatible with a large number of hypotheses, such as polytheism or a god of limited power, that are as plausible as or more plausible than monotheism—the argument from design continued to be very popular in the 19th century. According to a more recent version of the argument, known as intelligent design, biological organisms display a kind of complexity (“irreducible complexity”) that could not have come about through the gradual adaptation of their parts through natural selection; therefore, the argument concludes, such organisms must have been created in their present form by an intelligent designer. Other modern variants of the argument attempt to ground theistic belief in patterns of reasoning that are characteristic of the natural sciences, appealing to simplicity and economy of explanation of the order and regularity of the universe.
Perhaps the most sophisticated and challenging argument for the existence of God is the ontological argument, propounded by Anselm of Canterbury. According to Anselm, the concept of God as the most perfect being—a being greater than which none can be conceived—entails that God exists, because a being who was otherwise all perfect and who failed to exist would be less great than a being who was all perfect and who did exist. This argument has exercised an abiding fascination for philosophers; some contend that it attempts to “define” God into existence, while others continue to defend it and to develop new versions.
St. Anselm (centre), terra-cotta altarpiece by Luca della Robbia, 15th century; in the Museo Diocesano, Empoli, Italy.Alinari/Art Resource, New York
It may be possible (or impossible) to prove the existence of God, but it may be unnecessary to do so in order for belief in God to be reasonable. Perhaps the requirement of a proof is too stringent, and perhaps there are other ways of establishing God’s existence. Chief among these is the appeal to religious experience—a personal, direct acquaintance with God or an experience of God mediated through a religious tradition. Some forms of mysticism appeal to religious tradition to establish the significance and appropriateness of religious experiences. Interpretations of such experiences, however, typically cannot be independently verified.
Religions typically defend their core beliefs by combining evidential, moral, and historical claims as well as those that concern human spirituality. Because these claims together reflect the religion’s conception of what knowledge of God is, they must be taken into account when endeavouring to establish whether any particular belief within the religion is reasonable.
The Abrahamic religions (Judaism, Christianity, and Islam) also appeal to revelation, or to claims that God has spoken through appointed messengers to disclose matters which would otherwise be inaccessible. In Christianity these matters have included the doctrine of creation, the Trinity, and the Incarnation of Jesus Christ. Various attempts have been made to establish the reasonableness of the appeal to revelation through the witness of the church and through signs and miracles, all of which are thought to herald the authentic voice of God. (This is the context in which Hume’s classic critique of the credibility of reported miracles must be understood.) Yet appeals to revelation by the various religions conflict with each other, and the appeal to revelation itself is open to the charge of circularity.
The Nativity, fresco by Giotto, c. 1305–06, depicting the birth of Jesus; in the Scrovegni Chapel in Padua, Italy. ART Collection/Alamy
Metaphysical issues
The idea of God
The claim that there is a God raises metaphysical questions about the nature of reality and existence. In general, it can be said that there is not one concept of God but many, even among monotheistic traditions. The Abrahamic religions are theistic; God is both the creator of the world and the one who sustains it. Theism, with its equal stress on divine transcendence of the universe and immanence within it, constitutes a somewhat uneasy conceptual midpoint between deism and pantheism. Deist conceptions of the divine see God as the creator of a universe that continues to exist, without his intervention, under the physical impulses that he first imparted to it. In pantheism, God is identified with the universe as a whole. Theism itself has numerous subvarieties, such as occasionalism, which holds that the only real cause in the universe is God; thus, all other causes are simply signs of coincidence and conjunction between kinds of events occurring within the created order. For example, heat is not what causes the water in a teakettle to boil but is simply what uniformly occurs before the water boils. God himself is the cause of the boiling.
An important object of metaphysical reflection is God’s nature, or the properties of that nature. Is God simple or complex? If omniscience, omnipotence, and beauty are part of the divine perfection, what exactly are these properties? Is timeless eternity part of God’s perfection? Can an omnipotent being will that there be a four-sided triangle or change the past? Does an omniscient being know the future actions of free agents? (If so, how can they be free?) Does an omniscient being who is timelessly eternal know what time it is now? God and the universe
Whatever may have been the influence of Classical philosophy on the Abrahamic religions, they have not, in general, accepted the Greek idea of the eternity of matter but have stressed the contingency of the universe as the free creation of God. It has been argued, most notably and influentially by Aquinas, that neither the eternity of matter nor the doctrine of creation can be established by reason alone; thus, the belief that the universe is not eternal and was created by God must be derived from revelation. Some, including Augustine, have claimed that God created the universe from a standpoint outside time; others claim that God, like the universe, is in time.
It is at points such as these in the philosophy of religion that philosophical arguments have less to do with establishing the truth of some proposition and more to do with working out a consistent and intelligible account of religious doctrine. At least since Augustine, philosophers in the Abrahamic religions have seen one of their tasks to be the achievement of a greater understanding of their own faith. They have examined the logical consequences of religious doctrines and sought to establish their consistency with the consequences of other beliefs, as illustrated in the remainder of this section. God and human action
Philosophical reflection on the nature of God has typically assumed that God is the sum of perfection and is omnipotent and omniscient. Questions have arisen not only about the exact meaning of these claims but also about their consistency with widespread beliefs about human beings, chiefly the belief that they usually act freely and responsibly and should be held accountable for their actions. If God, being omniscient, knows the future, then God presumably knows what each person will do in the future. But if these actions are known by God, how can the person be free not to do them? And if the person is not free not to do them, how can he be held accountable for what he does? Even more difficult, perhaps, is the question: If God is omnipotent and exercises providential control over his creation, how can people be other than puppets?