Pius IX’s first encyclical was Qui pluribus (On Faith and Religion, 1846). It calls for moderation in the extreme claims made by the parties of ‘faith’ and of ‘reason’:
although faith is above reason, no real disagreement or opposition can ever be found between them: this is because both of them come from the same greatest
THE LIMITS OF REASON II: VATICAN I
source of unchanging and eternal truth, God. They give such reciprocal help to each other that true reason, shows, maintains, and protects the truth of the faith, while faith frees reason from all errors and wondrously enlightens, strengthens, and perfects reason with the knowledge of divine matters.1
The encyclical criticizes those who speak
as if religion ... were ... a philosophical discovery which can be perfected by human means. The charge which Tertullian justly made against the philosophers ..‘who brought forward a Stoic and a Platonic and a Dialectical Christianity’ can ... aptly apply to those men ... Our holy religion was not invented by human reason, but was ... revealed by God; ... religion ... acquires all its power from the authority of God who made the revelation, and ... can never be arrived at or perfected by human reason.1  
This is directed against those who sought to shore up the ‘public’ character of Christian revelation by showing that it meets the officially pervasive criteria of Kantian moral or practical reason. In an era of rising doubt, the temptation to be too apologetical is hard to resist.
Anton Gunther was an Austrian philosophical theologian who wanted to defeat Hegel and pantheism. He sought to demonstrate the reasonableness of faith in the Trinity. In Singulari quidem: On the Church in Austria, Pius IX singles out rationalism for disapprobation. Pius IX criticized Gunther in his 1857 Brief Eximiam tuum for making faith so reasonable that reason and faith become modes of the same intellectual act. The 1864 Syllabus of Errors (which, contrary to popular belief, does not list electric light as one of the errors of modernity) has as an appendage Quanta cura, which stigmatizes pantheism, indifferentism and rationalism.
Vatican I (1869-1870): Dei Filins
The teachings of Gregory XVI and Pius IX thus already sketch most of what will be promulgated at the ecumenical Council Vatican I. Vatican I (or the First Vatican Council) will promulgate two decrees. The first, Dei Filius, deals with faith and reason, while the second deals with the Church and defines the conditions of papal infallibility. The authors of Dei Filius drew upon the above-mentioned Briefs and encyclicals. In its original drafting, by J. B. Franzelin, Dei Filius was directed in an obscure philosophical way against the intricacies of metaphysical systems, like emanationism (a recondite version of pantheism which gave seminary professors a headache). After this draft was rejected, it was rewritten by Joseph Kleutgen (1811-1883) so as to address the great contemporary problems of atheism and agnosticism. Dei Filius was written by clear-minded Thomists to defend Christianity against those who would redefine it as ‘private opinion’ or permit it only to speak in the moderate tones of a scientific civil servant-university professor.
The Prologue to Dei Filius gives a ‘declinist’ history of the present-day dilemmas. Reformation Protestantism has devolved into ‘a multiplicity of sects’, leaving many without faith in Christ and regarding the Bible as ‘the inventions of myth’. This gave rise to ‘rationalism or naturalism’, which denies that anything exists outside and above ‘nature’. The denial of the supernatural then spawned ‘pantheism, materialism and atheism’, which generate irrationalism and immoralism.
Chapter 1 of Dei Filius affirms that God created the world ‘by an absolutely free plan’. The god of pantheism creates by a necessity of his nature, or simply because that is how such a god rolls. The Christian God creates ‘to manifest his perfection’, and does so freely. Chapter 2 is ‘On Revelation’. It asserts that God ‘can be known with certainty from the consideration of created things, by the natural power of human reason’. It does not prescribe any particular proof of the existence of God. It does not affirm that human beings might potentially be able to prove that God is. Rather, it says that God ‘can be known with certainty’ from ‘created things’. We can know God by rational inference from ‘things’, like human beings, dogs and stars. Since the chapter is ‘On Revelation’, these remarks mean that as God is revealed to human reason through God’s creation, like an author is revealed by his work, so God can be known from created things (here the Decree cites Rom. 1.20). The opening sentences of the Decree are about natural revelation, or God’s creation.
It goes on to speak about supernatural revelation, or those things exhibited to faith. In the first Question of the Summa, Thomas Aquinas notes that even those things about God which can in principle be known by reason were supernaturally revealed by God. Effectively paraphrasing Thomas’ article, the Decree adds that God ‘reveal[ed] himself to the human race by a ... supernatural, way ... It is ... thanks to this divine revelation, that those matters concerning God which are not of themselves beyond the scope of human reason, can, even in the present state of the human race, be known by everyone without difficulty, with firm certitude and with no intermingling of error’. Just as Thomas does, the Decree notes that the purpose of God’s revealing even those things which pagans could have guessed at about God is that the purpose for which the human race was made - to see God - transcends their natural powers.
God reveals to the eyes of faith even some things which reason could know. The Decree states that ‘one must hold revelation to be absolutely necessary’ to humanity because ‘God directed human beings to a supernatural end’. This is against diminishing the human journey to a path which we could naturally reason our way through. The purpose of humanity is to transcend itself and know the supernatural God, who exceeds anything which we could see or know naturally.
Moderns are interested in the psychology of faith. Focusing on the psychology of faith, or as faith as something interesting about me, can come at the expense of considering faith as a gift, or as something from God. This loses sight of the truth
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that I cannot give myself faith, I can only open myself to it or co-operate with it. If faith is not natural but a supernatural way of knowing and seeing the supernatural being of God, then I cannot leap or jump into it for myself. I cannot even pick it up and find it for myself, like poor Gollum with his ‘birthday present’ of a ring. God is too weird, too transcendent to be picked up for ourselves. Chapter 3 of Dei Filius states that faith is a ‘supernatural virtue’, that is, a virtue given by the grace of the Holy Spirit. By ‘means’ of this supernatural virtue, ‘we believe to be true what He has revealed, not because we perceive its intrinsic truth by the natural light of reason, but because of the authority of God himself, who makes the revelation and can neither deceive nor be deceived’.8
This assertion is balanced by the affirmation that the ‘internal assistance’ of the Holy Spirit, that is, supernatural grace, is ‘linked’ to ‘external indications’, especially the ‘miracles and prophecies’ of ‘Moses, and the prophets, and especially Christ our Lord himself’.9 Dei Filius did not intend to forfeit the external evidence for Christianity or to withdraw Christian faith from history.
The point here is to avoid defining faith purely on internal grounds, as a private sensation or conviction: ‘the assent of faith is by no means a blind movement of the mind’, the decree states; rather, we keep our eyes open and observe natural things and historical facts in the very act of believing the supernatural God. And ‘yet, no one can accept the gospel preaching in the way necessary for achieving salvation without the inspiration and illumination of the Holy Spirit, who gives to all facility in accepting and believing the truth. And so faith in itself ... is a gift of God’.10 No one can ‘achieve justification’, nor ‘attain eternal life’, ‘without faith’.11
So far, most of Dei Filius has been about theological epistemology: it is about how we know God, by faith and by reason. In Chapter 4, ‘On Faith and Reason’, we find a distinction between how we know, the source of our knowledge and belief and what we know, the object of knowledge and belief. It states, ‘there is a twofold order of knowledge, distinct not only as regards its source but also as regards its object. With regard to the source, we know at the one level by natural reason, at the other level by divine faith’.12 Knowledge of God occurs at two levels, through reason and through faith. ‘With regard to the object, beside those things to which natural reason can attain, there are proposed for our belief mysteries hidden in God.’13 The text moves beyond theological epistemology to the metaphysics which determines it: natural reason cannot tell us all we wish to know about God because God is mysterious. Therefore, some things about God must simply be believed, and cannot be known or proven.
Reason can ‘achieve by God’s gift some understanding ... of the mysteries, whether by analogy from what it knows naturally or from the connexion of these mysteries with one another’: so theology is never wholly in the dark about God. Nonetheless, natural human ‘reason is never rendered capable of penetrating those mysteries’ in * 11  
the way it can get inside natural objects. Even revealed mysteries of their nature (of the nature of God) remain impenetrable: ‘they remain covered by the veil of that same faith’ which ‘accepted’ them, and ‘wrapped ... in a certain obscurity’. This must refer to the mystery of the Holy Trinity. We can give analogies for the Trinity, as Augustine did with his triad of memory, will and knowledge, but such analogies must not be engineered to explain the Trinity or include it within some rational and total narrative. It makes us think of Winston Churchill’s description of Russia as ‘a riddle, wrapped in a mystery, inside an enigma’. In the case of the Trinity, faith does not make us see more, but it makes us see that we see less, that is, makes us recognize a mystery when confronted with one.
Reason and faith are different ways of knowing. Reason and faith know God under distinct aspects. But they know one and the same God so that what faith knows about God and what reason knows about the same God cannot contradict each other. Both creation (reason) and grace (faith) issue from the same God: ‘Even though faith is above reason, there can never be any real disagreement between faith and reason, since it is the same God who reveals the mysteries and infuses faith, and who has endowed the human mind with the light of reason.’
Dei Filius was not aimed against secular philosophies. It was written to warn Christians against being conformed to the mind of the age. It reminded Christian thinkers that faith and reason are distinct, balance one another and work in harmony.
- 1. Why did many nineteenth-century French people become traditionalists after the French Revolution?
- 2. What is the key concept in Dei Filius?
- 3. Is Dei Filius directed more against rationalism or against traditionalism?
- 4. Can Christianity influence public life if it cannot make evidential and argumentative claims about its truth?
Aidan Nichols, O.P., From Hermes to Benedict XVI: Faith and Reason in Modern Catholic Thought (Leominister: Gracewing, 2009).
‘Dogmatic Constitution on the Catholic Faith: Dei Filius’, in Norman P. Tanner (ed.), The Decrees of the Ecumenical Councils: Volume II: Trent to Vatican II (London: Sheed and Ward, 1990).
-  Pius IX, Qui pluribus: On Faith and Religion, §6.
-  Pius IX, Qui pluribus, §7.
-  Pius IX, Singulari quidem: On the Church in Austria (1856), §6.
-  Decrees of the First Vatican Council, Dei Filius (1870), Prologue, §§5-7.
-  Dei Filius, I.3.
-  Dei Filius, 2.1-4. Compare Thomas Aquinas, Summa theologica I, q. 1, a. 1.
-  Dei Filius, 2.4.
-  8Dei Filius, 3.2.9Dei Filius, 3.4-5.10Dei Filius, 3.6-7.
-  Dei Filius, 3.9.uDei Filius, 3.2.13Dei Filius, 3.3.
-  Dei Filius, 4.4.
-  Dei Filius, 4.5.