Western concepts of God have ranged from the detached transcendent demiurge of Aristotle to the pantheism of Spinoza. Nevertheless, much of western thought about God has fallen within some broad form of theism. Theism is the view that God is unlimited with regard to knowledge (omniscience), power (omnipotence), extension (omnipresence), and moral perfection; and is the creator and sustainer of the universe. Though regarded as sexless, God has traditionally been referred to by the masculine pronoun. Concepts of God in philosophy are entwined with concepts of God in religion. This is most obvious in figures like Augustine and Aquinas, who sought to bring more rigor and consistency to concepts found in religion. Others, like Leibniz and Hegel, interacted constructively and deeply with religious concepts. Even those like Hume and Nietzsche, who criticized the concept of God, dealt with religious concepts. While Western philosophy has interfaced most obviously with Christianity, Judaism and Islam have had some influence. The orthodox forms of all three religions have embraced theism, though each religion has also yielded a wide array of other views. Philosophy has shown a similar variety. For example, with regard to the initiating cause of the world, Plato and Aristotle held God to be the crafter of uncreated matter. Plotinus regarded matter as emanating from God. Spinoza, departing from his judaistic roots, held God to be identical with the universe, while Hegel came to a similar view by reinterpreting Christianity. Issues related to Western concepts of God include the nature of divine attributes and how they can be known, if or how that knowledge can be communicated, the relation between such knowledge and logic, the nature of divine causality, and the relation between the divine and the human will.
Sources of Western Concepts of God
Sources of western concepts of the divine have been threefold: experience, revelation, and reason. Reported experiences of God are remarkably varied and have produced equally varied concepts of the divine being. Experiences can be occasioned by something external and universally available, such as the starry sky, or by something external and private, such as a burning bush. Experiences can be internal and effable, such as a vision, or internal and ineffable, as is claimed by some mystics. Revelation can be linked to religious experience or a type of it, both for the person originally receiving it and the one merely accepting it as authoritative. Those who accept its authority typically regard it as a source of concepts of the divine that are more detailed and more accurate than could be obtained by other means. Increasingly, the modern focus has been on the complexities of the process of interpretation (philosophical hermeneutics) and the extent to which it is necessarily subjective. Revelation can be intentionally unconnected to reason such that it is accepted on bare faith (fideism; cf. Kierkegaard), or at the other extreme, can be grounded in reason in that it is accepted because and only insofar as it is reasonable (cf., Locke). Reason has been taken as ancillary to religious experience and revelation, or on other accounts, as independent and the sole reliable source of concepts of God.
Each of the three sources of concepts of God has had those who regard it as the sole reliable basis of our idea of the divine. By contrast, others have regarded two or three of the sources as interdependent and mutually reinforcing. Regardless of these differing approaches, theism broadly construed has been a dominant theme for much of the history of Western thought.
Medieval Thought
Working from Judaism, Maimonides (1135-1204) accepted creation rather than an eternal universe. He drew from philosophic traditions to formulate three proofs based on the nature of God, and these were developed further by Aquinas. Following Aristotle Maimonides demonstrated the existence of a Prime Mover, and with some inspiration from Avicenna, the existence of a necessary being. He also showed God to be a primary cause. Though he considered God's existence demonstrable, he held that nothing positive could be said about God.
Unity
Monotheism maintains that there is one God. To this Christianity adds that there is a threefold distinction within one God. Stated roughly, God is one substance in three persons. Aquinas argued that there cannot be two gods because neither would be absolutely perfect since one would have a quality that the other lacked (Summa Theologica Ia, 11, 3). Richard Swinburne says that theism is a simpler hypothesis than polytheism, the latter positing more beings with various capabilities and relations. Theism is therefore more likely since simpler hypotheses turn out to be true more often. Moreover, the universe exhibits a unity, in its universal natural laws for example. This unity argues for one deity as its originator (The Existence of God, 1991, pp. 141-2).
