2.2 Christian theism

The first centuries of Christianity were profoundly influenced by the Second Temple Jewish monotheism. Much philosophical effort effort was put forth to comprehend, not theism itself, but rather the natures and relations of Jesus and God. The influential thinkers here were Justin Martyr, Tertullian, Origen, Athanasius (culminating in the Nicene Creed), and Augustine. Their formulations included many individual terms of Greek philosophy, but these terms were not included within a systematic framework.

The first comprehensive attempt to understand something like theism in terms of Greek philosophy was that of Plotinus (204-270), who used ideas from Plato to view the creation of the world as an emanation from God the Absolute One. In this ‘Neoplatonism’, the Absolute One contains no division, distinction or multiplicity, not even the distinction between being and non-being. Yet by emanation or ‘overflowing’, it produces a created universe that descends by degrees eventually to the material level. The world is not created from love, and it does not even act freely, but follows necessarily from the One. This Neoplatonism proved attractive to many Christian and Islamic thinkers such as the Alexandrians, Augustine, and pseudo-Dionysius, even though it was initially opposed to Christianity and not generally accepted as orthodox because of its non-dualist and gnostic tendencies. It was not thought to allow sufficiently for the distinction between God and humans. Also the route it described for religious salvation was through esoteric knowledge and mystical union rather than by means of a religious or social life accessible to everyone.

Thomas Aquinas (1225-1274) was the first to take seriously within Christianity the works of Aristotle. Islamic philosophers and the Jewish monotheism of Maimonides had already been influenced Aristotle’s books. Aquinas showed how Aristotelean concepts may be used to formulate a metaphysics in which Christianity may be understood. At the time, the general opinion was that a Platonic formulation would be easier, but Aquinas showed that, with only a few extensions, Aristotle’s approach was very useful. Aquinas used Aristotle’s analysis of organisms in terms of function and form. He again described these functions as caused by vegetative, animal and rational souls. However, he decided that since forms must always be forms of some substratum, that substratum cannot be matter in general (as Aristotle thought) but instead must be whatever exists that has no form or property. The underlying substratum or substance must therefore be pure potency: just and only that capacity to receive and embody forms. Aquinas viewed the causal powers of objects and organisms as arising from the forms (that is, souls) of those beings, since pure potency is too indeterminate to generate specific powers. This view requires attributing causal powers to forms which must therefore be somehow more than ‘shape’ and ‘structure’.

In order to adapt Aristotle’s philosophy to Christian theology and the survival of bodily death, Aquinas took the rational soul of humans to be not a form of the physical body but rather a form which is immaterial in some way. He was not clear concerning the nature of this immateriality, only saying for example, that an angel can be formed as an immaterial substance by conjoining an intellectual soul with an ‘act of existence’. A whole person needs also a physical and biological body to function, but the intellectual soul can persist somehow as some immaterial aspect and be influential as a ‘formal cause’ in some way.

God was conceived by Aquinas in the full theistic manner as Perfect and Immutable Being Itself, Truth Itself, along with the attributes of Impassibility, Transcendence, Immanence, Omnipotence, Omniscience and (Omni)benevolence.^2.1What is new with Aquinas is that God is conceived as Pure Act and is completely devoid of potentiality.^2.2 ‘Love’ gets added in as one more perfection. We may reasonably ask, however, whether Aquinas had the correct way of conceiving God to be a creative power, considering that the formulation of ‘Pure Act’ excludes all concepts of potentiality and hence of power and therefore partly contradicts the view of God as powerful.

Aquinas’ philosophy (Thomism) subsequently became orthodox within the Catholic church. Because it was based on Aristotle’s approach rather than that of Plato, we can argue that this scholasticism laid the first foundations for a scientific revolution that starts not with God but by examining nature itself.