St Mary's In-Depth Theology Course

On Reason in Christianity

We cannot know much about Thomas Aquinas (1225-1274 CE) and his product Thomism without knowing something about Aristotle in a previous civilisation (384-322 BCE). Scholasticism, or the application of reason into Christianity, is seen as a major foundation for Western Christendom, for Roman Catholicism and therefore offshoots like the Anglican stream and beyond to those who uphold reason in religion. This reason is not just that of the long absorbed Greek culture of the New Testament period, but ancient Greek culture with its own argument about methodology.
If we look after Socrates (470-399 BCE) at Aristotle, then Plato (429-347 CE) is involved by contrast, and we also need to look at the Christianity of Aquinas's day, largely defined by Augustine of Hippo (354-430 CE); and then included must be the released and rival foundations of reasoning placed into religion as by the Islamic builder upon Aristotle - rivalling Aquinas and Anselm of Canterbury (1033-1109) - namely Avicenna or Ibn Sina (980-1037).
1700 hundred years after Aquinas it may seem strange to contemplate a Christianity without this accepted import of reason, so we also need to consider Christianity before Aquinas and the Middle Ages synthesis of revelation and reason. Also, Aquinas was not received without opposition: conservative theologians of his time opposed the use of reason as a support for revelation. Revelation was enough, and it was Christian, whereas reason was seen as Pagan and of a different ethos altogether.
The Persians and Arabs had translated classical culture and used it; diminished Byzantium institutions still stored it in Greek. Classical culture had never entirely vanished within European Christendom; it was just that Europe had an existence more local to itself in only the memory of Roman occupation and culture: feudal Europe simply had no place for that learning before Arab culture burst on to the scene due to the expansionary aggression of Christendom. In Christian institutions - the monasteries, universities and churches - the principal intellectual impact was until then Augustine of Hippo (354-430 CE), who rejected classical reasoning.
The extraction from and decline of Islamic culture, and the rise of the West, released Arabic translated and developed Greek sources for translation into Latin. The translated major works of Aristotle struck Europe as a serious and developed competitor for an already regulated Christianity. So Aquinas the theologian absorbed it into the Christian scheme.
The question about absorbing reason into Christianity is this: did it save Christianity, making it broad and open and practical in positively discussing the world, or did Chrsitianity absorb something that was always self-contained and eventually going undermine its host as its original conservative opponents feared? After all, what is the later Renaissance other than the confidence of reason emerging out of its Christian host, prior to the Reformation that would turn Christian institutional life from the one institution in any geographical area to the many, a weakening that allowed reason its emergence?
Aristotle (384-322 BCE) was an incredibly wide range expert thinker except for mathematics. He joined together the pre-Socratic cosmologists, Socrates (470-399 BCE) himself (who said thought produces standards of right and justice) and Plato (who elevated Socrates' ideas to thought about purity). Aristotle though had both feet on the ground, and was both empirical and practical: he wanted to understand the world we stand upon and are surrounded by, and like Socrates and Plato believed in reason. He rejected Plato's approach of an independent world of Forms beyond space and time that mirrored in perfection what we experienced in imperfection. There was too much mystery, mysticism and fancy in Plato's construction: Plato undervalued this world of ours. Yet Aristotle agreed with Plato that we needed to know the essence of things and that the aim of knowing was to discover universal principles, just not to locate them in another world from ours. Like Plato he did believe in pure Forms but these forms were found in the objects themselves. Reason can discover the essence, the pure form, of these objects, living and otherwise. So what is the pure form of horse? What is the pure form of white? For Plato it was in a spiritual existence located elsewhere, but for Aristotle they were reasoned out. To get to these universals, then, you took in the varieties and imperfections of data and you reasoned the universal forms.
By seeing pure forms as other worldly, Plato favoured mathematics and metaphysics; whereas Aristotle, by seeing pure forms within, favoured the earliest forms of physics, biology, zoology, chemistry and any science based on observation. However, Aristotle did not understand the function of experiment. So if he observed maggots emerging in the dead human body, and reasoned that this is what death produced, he forgot a little experiment of covering the body to show that maggots actually did not self-generate - they came from eggs laid by flies. So he wasn't a proper scientist; rather, he was an observer.
Aristotle also thought that ethics came from reasoning. If you examined life, you could make it well. Apply intelligence rather than tradition and authority and you could get good decisions. Of course humans were passionate, and you should take account of that, but not just give way to desires. If you were trained, you could regulate your desires, and reach better decisions. Like Plato, Aristotle believed that politics could be regulated into law, and law was rational (beyond the passions) and therefore reasoned and ethical. Tyranny and revolution were anti-Law and thus unethical. Also the rich were too rich to submit to Law, so that growing up without learning obedience they tended to become despots; whereas the poor never learnt reasoning and should therefore be treated like slaves. Aristotle was a man of the middle way and the middle class.
Augustine of Hippo (354-430 CE) rejected the autonomy of reason, which was the principal claim of the self-contained classical humanism. Going back from him, Christianity in its time of initial expansion appealed to the sense of exhaustion with the here and now. Aristotelian reason and science was overwhelmed as it did nothing for a sense of loneliness in that despotic social setting, and people preferred the Platonic mystery cults with magic and mysticism for escapism and prediction. Christianity did what the platonic mystery cults and all the magic did but only much better, with its God that offered a personal interest and gave an encounter with its saviour figure. Both the Hebrew world and the Greco-Roman culture were deeply troubled, and many a trader and whole baptised families could use Christianity as an ethical badge as they moved up and down trading routes. Gentiles who admired Judaism's one God and the predictions of the perfect world to come could now join their own version of something similar, far more rational than polytheism and yet just as vivid and very Platonic.
Christianity when it had been Judaic had the same fate as the Jewish messianic cults: it collapsed; Christianity when Gnostic had the same outcomes as the various Gnostics: plural, with self-concerned cultic behaviours; but Christianity just loved Hellenism, because it elevated this world into the world beyond, and it crystallised the Platonic in its own Hellenistic scheme. This is what would appeal to a later Roman Emperor, sooner or later.
The other aspect that Hellenism Christianity absorbed was the Stoic idea that the world consisted of a single society, of equal people, and had a universalist outlook and a principle of order - a divine reason or logos, of which we were a part. Stoicism was a principle philosophy of the Greco-Roman world. The Stoics were optimistic regarding human reason and about ethical outcomes, just like Aristotle, Plato and Socrates. Christianity reused Greek concepts (such as perfect forms, and in combination like Truth and Beauty, now held within the mind of the one God), and took the ethical argument system and turned it into theology.
But not Augustine of Hippo (354-430 CE), who turned this early synthesis of Hebraic and Greek into a theology focussed upon revelation. After all, once reasoning becomes under God, it is God who ends up revealing it and Augustine stressed God. Humans then start to become less capable. Augustine was no optimist when it came to humanity: we were all caught up in original sin, his take from the Bible (but not a doctrine in the Bible). This tension, between the potentially good and inevitable evil, and indeed between revelation and reason, was always present in Christianity. Nevertheless, original sin once defined means incabability, and reason will be as flawed as its human producers.
In 410 CE the Visigoths sacked Rome, and the classical world was traumatised. Augustine was fifty years old. Pagans blamed the Christians and the Christians wondered why even the righteous were suffering. There was thus no Kingdom of God on earth. So Augustine took up the theme, and his City of God was a heavenly city, not a city on earth. Thus we had Plato again. But he went further. Not all were saved by Christ, but only some who had received the gift of faith and therefore eternal life. In the earthly city most were destined for eternal punishment. We could not reason our selves into the good, but depended on the grace of God. So revelation went right into the ethical sphere. It also went right into the intellectual sphere: reason was guided by faith and secular knowledge was of little worth. Thus the believer who would be saved studied the Scriptures for the clues of God's revelation and this overturned the classical view of reason.
So to attempt to synthesise reason back in was going to be a huge task. But faced with the outflowing intellectual and cultural results of Arab learning, this was perhaps necessary. The Germanic world had not been able or even concerned to restore Greek and Roman culture that was once all pervasive. Now there was a coherent challenge, the prospect of an intellectual competitor to the established intellectual order.
The Mediaeval world view demoted any reason that was not supported by revelation. Indeed it has a Gnostic imprint within, representing the ambiguity of the Gospel of John and New Testament Greek times: Spirit was superior to matter. The earth was pretty much base, standing just above hell. So perfection was found to be high up, literally, and imperfection low down, and you might say that they were connected by snakes and ladders (although the game of snakes and ladders was Hindu!). The celestial hierachy was fixed. From the bottom you had lifeless and soulless stones; then plants, whose primitive soul allowed reproduction; then animals, with motion and sensation; then humans, who understood revelation imperfectly, the lowest beings who could climb upwards towards the heavens when removed of their sin; then angels, who understood God without difficulty; then the pure being of God. This chain was also a chain of communication of knowledge and control. It carried a geography. Aristotle with Ptolemy had also believed in spheres of existence, a motionless earth with planets in their own spheres (moon, Mercury, Venus, the sun, Mars, Jupiter and Saturn), but now inhabited full of Christian mythology as well as the astrological. Above the planets were the stars and then three heavens, the outer Empyrean heaven being where God and the elect were found and where knowledge was the purest. In terms of the human section of this hierarchy, there was a human hierarchy itself, and so feudal life was as God and Christ willed. The Kings had divine right, and everyone knew their place.
Thomas Aquinas had to join Christianity with an Aristotelian system that said that the universe had no beginning and the soul was not immortal. Christianity said it began and held that the soul was immortal. It had to fuse a view of the human as reasoning towards pure knowledge with a view that placed pure knowledge only with God.
Aquinas's main view was simple: Revelation and reason cannot contradict each other. If reasoning is pure and correct, it will agree with revelation. How could they be different? There was no reason, so to speak, to be afraid of reason, as it was just another route to God. Thus, once again, Aquinas reasserted human reason, the human senses, and physical reality. If reason disagreed with revelation, it had not employed a necessary argument.
Aquinas also used Aristotle in his own five proofs of God's existence. Aquinas for example used Aristotle's view that an object cannot move itself. This meant going back as something else moved the thing under consideration, until reaching the prime mover, being God. It is for the proofing of the existence of God that Aquinas is best known.
So his First Argument, then: Motion

  1. Objects are in motion.
  2. Nothing can move itself and so its motion is caused by something else.
  3. This chain cannot last forever.
  4. So there is a first, unmoved mover.
  5. God is that unmoved mover.
  6. God exists.

[Note that strictly speaking, 1 and 6 are superfluous to the proof]
Second Argument, Causality

  1. Events happen.
  2. Other events cause events.
  3. This chain cannot last forever.
  4. So there is a first, uncaused cause.
  5. God is the uncaused cause.
  6. God exists.

[Note that strictly speaking, 1 and 6 are superfluous to the proof]
Third Argument, Contingency

  1. Contingent things exist.
  2. Contingency means they had a time of not existing
  3. There was an empty time when nothing contingent existed.
  4. But if there was nothing, there would not be anything ever.
  5. The uncontingent must exist.
  6. God exists.
Fourth Argument, Properties That Come in Degrees

  1. Objects have properties.
  2. Properties exist to greater or lesser degrees.
  3. There exists some object that has properties to the maximum possible degree.
  4. Only God can possess all properties.
  5. God exists.
Fifth Argument, From Design

  1. Objects that behave towards an end may or may not have minds.
  2. An object that acts for an end without a mind needs a mind to set up that behaviour.
  3. An object with a Mind designs the behaviours of the mindless towards an end.
  4. God is that Mind.
  5. God exists.
At this point we should introduce another thinker of reason, Anselm of Canterbury (1033–1109). Anselm employed The Ontological Argument.

  1. The fool understands the definition of God but denies that God exists.
  2. The fool accepts that you can think something, like a painting exists in the mind before it is painted.
  3. If the painting exists, then it is understood all the better
  4. God - a being than which none greater can be conceived can be understood in the mind
  5. But God - a being than which none greater can be conceived cannot exist only in the understanding but must also exist in actuality.
  6. God exists.
Aquinas has an important Muslim competitor. The first recorded ontological argument for the existence of God came from Avicenna (980-1037) in the Metaphysics section of The Book of Healing, being the contingency and necessity argument (Imakan wa Wujub). Like Aquinas he used Aristotle (and developed from him), and set out to reconcile rational philosophy with Islamic theology. His writings were released into Western Europe. Half of his writings are versified; he produced some 540 volumes with 240 or so survived.
Like Aristotle Avicenna was a very wide ranging thinker among both Muslim and Scholastic thinkers, covering among many matters the fundamental concept of momentum in physics, aromatherapy, logic, engineering, geology, medicine and theology. Avicennism is his Persian Islamic school of philosophy in the Islamic golden age (until the 1400s CE). His full name was Hussain ibn Abdullah ibn Hassan ibn Ali ibn Sina or Ibn Si-na-' for short.
He memorised the Qur'an when seven years old; he read Aristotle some forty times, but despite much being memorised the meaning was obscure until a small booklet by al-Farabi broke his mental impasse. One method for studying philosophy was to leave his books, carry out wudu, go into the mosque, and do salah (prayer) until receiving inspiration. He worked into the night and sometimes a dream would lead to a solution.
Ibn Sina discussed the pure existence of the soul. His argument for God is both ontological and cosmological, in that necessary existence leads to a Necessary Existent and because a contingent existent cannot stand alone and must begin with a non-contingent Necessary Existent.
  1. There is essence (Mahiat) and existence (Wujud)
  2. Existence cannot be derived from essence alone
  3. Form and matter cannot originate the movement of the universe or the actuality of existing things.
  4. The cause of existence is down a chain of existence
  5. A chain of existence cannot actually be infinite and so there must be a first existence.
  6. This first existent being is wholly simple and one - God.
  7. The first essence thus is its very existence - God.
  8. God is First Cause: the Wajib al-Wujud (necessary existent)
Against his Christian critics, Aquinas even went further in his upholding of reason: that in nontheological questions not affecting salvation, reason and experience were entirely to be trusted. To affirm the intellect was to love God, for God had made the intellect to be used. Thus the intellect was not to be suspected, but was to be used to gain information about the natural and the social order.
Yet Aquinas was supremely confident that truth was one and indivisible, and that truth was affirmed by faith.
Still, confidence in this facilitated a willingness to handle the translations of scientific material becoming available. Perhaps Aquinas was simply a man of his time. For example, philosophy was shifting towards an understanding of nature as much as dealing with divine wisdom, thanks to Albertus Magnus, a Dominican (1206-1280) and Thomas Aquinas was his student at the University of Paris. But still someone had to do the work of synthesising reason and religion. An interesting chap was Robert Grosseteste (1175-1253) who became Chancellor of Oxford University. He said mathematics could be used for the purposes of studying the natural world such as light refraction (whereas mathematics had been Plato's side of things, a study of the pure). Another person who studied refraction, investigating what the Muslims had done, was Roger Bacon (1214-1294) and carried out his own experiments with optics and found that light travelled faster than sound. Yet the ghost of Plato was all over them, because for them different scientific laws existed in the purity of the heavens. Science was firmly within theology, even though they had started to experiment.
Scholastics did employ a critical approach at times, and were careful in their reasoning. They simply never escaped the overarching viewpoint that the natural order depended upon the supernatural order. Reason just had to conform with Scripture as interpreted by the Church. The light of reason needed a divine light.
It was when thinkers rejected a pure world above and argued for the unity of scientific laws that reason began to break out from the hold of theology. Nature was uniform, they decided. The universe became not finite and limited but infinite. Grades of perfection were of no interest to more modern thinkers in science or philosophy. Such was to lead to criticism of the social order as divinely ordered and the Church too.
Nevertheless, Thomism or neo-Thomism survived the decline of the Mediaeval world view about spheres and perfections: in that many still argued that a united and infinite knowledge still needed a pure guarantor of reason. Truth needs Truth with a capital T, and there is God the guarantor.
Reason began to break out from Christianity at the Renaissance. Then the Reformation pluralised Christian institutions and began the process of removing their power. The Enlightenment, and rules of academic discourse subject by subject meant the release of reason into its own domain once again.
Thomism was foundational for the Western Church, but not exclusive. Yet the Roman Catholic Church defended Thomism long past modernity: in 1893, Pope Leo XIII issued an encyclical letter Aeterni Patris, and this made the stance of St. Thomas Aquinas normative for the Church. But whereas Thomism was progressive and argumentative, this approach was defensive, institutional and based on students copying from books of overbearing philosophical detail rather than debate. Thomism became, institutionally, an anti-modernist neo-scholasticism. There was thus something of a rapid deflation of Thomism after Vatican II. Even since then traditionalists still use neo-scholasticism and Thomism politically, and we see a rationality of reasoning and chain of reasoning towards preset divine positions defended.
Thomism had wider power because the rationality of the natural world was ultimately upheld by the divine: G.K. Chesterton's book Orthodoxy (1908) had a chapter called 'The Suicide of Thought' and C.S. Lewis rewrote a chapter of Miracles (originally 1947) and called it 'The Cardinal Difficulty of Naturalism'. Miracles was republished in 1960. Both asserted that there is no first cause of reasoning from below - called naturalism. The first cause of reasoning, to prove reasoning is reason, must come from God: naturalism falls back on itself, and the brain processes are only that, so that the mind needs a divine mind and not unrelated material stuff.
This is seductive but is the nonsense of irrelevant foundationalism. It is called the fallacy of division, that a part must have the qualities and substance of the whole. You shift backwards to first causes that are unrelated arguments; the first relevant move is the phenomena being dealt with, not some unrelated argument. An argument of the necessary phenomena produces its own results and survives by feedback: and of course it becomes supported by experiment that returns the argument, or simply by the logic of the argument in situ. We are always 'inside' what we do. Phenomenology undermines Thomism!
Furthermore, what we now understand is self-generating mathematics, thanks to Alan Turing, illustrated by John Conway's The Game of Life. C. S. Lewis said the Gulf Stream cannot map itself, or ashes tipped out of his pipe explain themselves that they are ashes out of his knocked out pipe (Lewis, 1967). Yes, but go back to the simplest relevant phenomena, and we do find this self-organising principle, and a chaotic outcome principle. For example, we cannot go 'before' time - we are always within, and time began as part of its own beginning.
It is goodbye to the pure Forms view, whether on earth or in Plato's heaven. Instead, irrational atoms and buzzing brain waves are quite capable of producing a rational world and rational thought respectively - going back one does not have to retain the composition of the other (fallacy of division); we are always where we are.
And this really is, or should be, the death of Thomism and indeed Avicennism. Energy and matter do intertwine, that there is the 'irrational' quantum world, time has a beginning wholly within itself, and the universe has a beginning wholly within itself. The first cause argument doesn't apply beyond what we have. Self generating mathematics guide complexity out of iterated simplicity, and this is what we observe in nature. What happens is not even predictable, after relatively few moves. There are systems that exist, and within them generating yet chaotic events, that lead to systems undergoing radical overhauls (for example, ice ages becoming warm periods and all without human impact). Evolution is a feedback loop for chaotically mutating life. More than this, the uniformity of application of some mathematical and scientific laws is gone at the very small and the very large. Thus the chain of causality breaks up, changes, splits, and loops back on itself. Also threatened is the notion of a simple, linear view of time, in the same way that space is bendy, even if time might fade away into an eventual meaningless over expanded and dead universe.
Divine cause, effect and intervention lies at the heart of Christianity, and the question becomes how to understand Christianity once this Thomist-centred - this synthesised Plato above and Aristotle below - scheme is unsustainable. For example, we might return to some of the thoughts of John A. T. Robinson, who was keen to overturn what had become of Thomism, or what he thought of it (perhaps overstressing the institutional power aspect). Is there something instead for personal approaches to faith: but at what cost to all that the logic behind doctrines?

Main Points

  • Consider Aquinas and then you need Aristotle; Ibn Sina also built on Aristotle; Anselm had another proof; there was also Socrates and Plato, and Aquinas synthesised reason when Augustine of Hippo rejected reason.
  • Aristotle was an observer, not a scientist, but his reason gave rise to experimenting.
  • The Muslim world preserved and developed Greek knowledge; Christian expansionism released reason into Christendom and it was seen by many as a threat.
  • Conservative theologians at the time rejected Aquinas's importation of reason, whereas later conservative theologians defended neo-scholasticism.
  • Arguments for God were all 'chain' arguments - by Aquinas, Anselm and Ibn Sina.
  • Whilst science still looks for the simplest and the intertwining in causes and effects, arguments now are about relevant phenomena: pure Forms involve the fallacy of division.
  • The implications for theology are widespread, and impact on those who claim the tradition of causal chain reasoning in religion.


  1. To what extent is 'narrative' and forms of 'postmodern' theology a cover for maintaining the Christian tradition as a package given the shift in science and philosophical reasoning and the difficulty regarding reason in religion in the sense that it existed in Thomism?


Perry, M. (author), Bock, G. W. (editorial associate) (1993), An Intellectual History of Modern Europe, Boston: Houghton Mifflin, 17-22, 26-31, 36-39, 40-49.

Lewis, C.S. (1967) 'De Futilitate' in Walmsley, L. (ed.) (2002), C.S. Lewis Essay Collection: Literature, Philosophy and Short Stories, London: HarperCollins, 267-8.

Schihl, Robert J. (1998?), Aquinas' and Anselm's Arguments for the Existence of God in Syllogistic Form, School of Communication and the Arts, Regent University Virginia Beach, VA [Online], Available World Wide Web, URL: [Accessed: Monday February 08 2010, 19:56].
Wikipedia editors (2009), 'Avicennism', Wikipedia, the Free Encyclopedia; last update 27 January 2010; Wikipedia Foundation [Online], Available World Wide Web, URL: [Accessed: Monday February 08 2010, 20:39].

Wikipedia editors (2010), 'Avicenna's Argument', 'Ontological Argument', Wikipedia, the Free Encyclopedia; last update 6 February 2010; Wikipedia Foundation [Online], Available World Wide Web, URL: [Accessed: Monday February 08 2010, 20:24].



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Adrian Worsfold

Pluralist - Liberal and Thoughtful