At the beginning of this work, we had pointed out the fundamental distinction between natural knowledge and supernatural knowledge in general concerning knowledge of God, further specifying that the former comprises common sense, life experiences, philosophy and particular sciences (cultural anthropology, psychology of religion, ethnology, sociology, the history of religions) while the latter comprises, besides the act of faith (common to all believers), theological reflection (which is proper of some intellectuals) and mystical experience (which is even more selective, inasmuch as it presupposes certain charisms).
Having made these distinctions, it is precisely the act of faith in Revelation that I have discussed, examining its constitutive characteristics under the prism of alethic logic. This has been a philosophical conversation which has taken into consideration that which Christian faith asserts about itself, that which it claims to be, i.e., how it is presented when speaking about itself.
And it should not be surprising that philosophy also treats the Christian ‘phenomenon’ (Christianity as an historical reality which is phenomenologically observable), given that philosophers (believers and non-believers alike) have always done this since the time when the religion of Christ was spread in the Hellenistic world: we can think of the anti-Christian polemics of the Neo-Platonists (Proclus, Porfirius, Plotinus), and even before that, of the clarifications and elaborations of the Church Fathers in their apologetics as an answer to the objections of the adversaries of Christianity (both from the Jews and Pagans), objections that often targeted the logical nature of the act of faith in Christian revelation (as in the case of Celsus) or the rationality of its contents (as in the case of Plotinus and Proclus).

To all those who held that Christianity was merely a social phenomenon reducible to superstitious attitudes (an irrational acceptance, i.e., not motivated, of novel religious and moral doctrines which were themselves unreasonable, absurd and unbelievable), the apologists and Christian polemists (Justin the Martyr, Tertullian, Origin) replied by analyzing the nature of the act of faith in the Gospel, pointing out its intrinsic rationality, in relation to their completely reasonable doctrinal contents: all of which could not have been brought about except through an epistemic critique, i.e., through philosophy.
Thus has it been for all subsequent centuries, even today: it is enough to recall important episodes in the history of philosophy such as the controversies concerning the relation between faith and reason during the Reformation and Counter-Reformation; the apologetic intent that guided Blaise Pascal in the writing of the unfinished work we know as the Pensées; the struggles of ‘Catholic Pyrrhonism’ and the anti-sceptical polemics of the Cartesians and anti-Cartesians (Cf. Livi, 2003d); criticisms of the British and French Enlightenment authors concerning Christian dogma and the developments of philosophical Deism; Kant’s distinction between ‘knowing’ and ‘believing’ in his Critique of Pure Reason; the dialectic of faith and philosophy in Hegelian logic; the anti-rationalistic reaction of Kierkegaard and his conception of ‘faith’ as ‘risk’; the various forms of Catholic fideism in the nineteenth and twentieth centuries; the hypothesis of the interpretation of philosophy itself as ‘faith’ by Karl Jaspers…
In the final analysis, there is no doubt that the philosophical analysis of the act of faith, carried out with the intention of recognizing its real connoted objects within their authentic formulation (Sacred Scripture and the Magisterium of the Church), has demonstrated a fundamental interest for philosophy both historically and theoretically.

In dealing with the act of faith in Revelation, I have emphasized the need to accurately distinguish between natural knowledge of the existence of God (common sense knowledge and metaphysical knowledge) and supernatural knowledge of divine mysteries (through revelation that God has made about his nature and his salvific plan); in fact, it is necessary to bear in mind that there is a conceptual confusion in ordinary language which deals with ‘faith in God’ and ‘believing in God’ almost always referring to natural knowledge of God (i.e., the certainty about God’s existence, proper of common sense), yet situated on the same level of the acceptance of the supernatural mysteries revealed by God.
If such a conceptual confusion is not overcome, any conversation concerning the relation between faith and reason will be bereft of those minimal requirements of rigour that would make it a constructive conversation; and the same rigour is required by those who reject the Catholic notion of faith and propose another one: either because they argue in favor of the exclusion of faith from the field of rationality, leaving space only for dialectical reason (rationalism), or because they intend to conclude their analysis of faith by eliminating the rational component in favor of a voluntaristic option which would not need reasons (fideism). In both cases, dialogue can only occur on the basis of explicit definitions of what is intended, once the Catholic notion of faith is jettisoned, by ‘faith’ in relation to ‘reason’.

The analysis here developed has also clarified the important distinction between the ineffable nature of God (which concerns his essence and his plan for salvation, mysteries which are inaccessible for natural reason and which remained veiled by symbols even when one achieves knowledge of them through faith in Revelation) and the certainty of his existence (certainty which provides the basis for natural religion and acts as a rational premise for the acceptance of supernatural revelation): ignoring this distinction has often led to confusing the ‘unknowableness’ of God (in his essence) with the refusal of admitting his existence, i.e., atheism; as well as exasperating beyond all limits the ‘negative’ character of mysticism.
The speculative advantage of these investigations and distinctions has been the disclosure of certain illegitimate presuppositions of modern and contemporary philosophical systems when dealing with the problem of God. Under the prism of what must be affirmed – speaking rigorously – concerning the rational nature of Christian faith in revealed mysteries, it becomes evident that modern philosophy has contributed – through ambiguous and misleading philosophical applications of the theological notion of ‘faith’ – to the introduction of conceptual confusion precisely where it is indispensable to have these distinction very clearly drawn.

Above all, it can be clearly seen that Kant, with his exclusion of the notion of God from the deposit of knowledge qualified as ‘objective’ (i.e., grounded on sensate experience and on the application of a priori forms: space, time, categories), has been responsible for the false and unfounded conviction – for too long shared by a large part of Western culture – that natural reason can not arrive at a rational certainty concerning the existence of God and that all the metaphysical proofs of the existence of God – including the Thomistic ways – are lacking any speculative foundation (Cf. Immanuel Kant, Kritik der reinen Vernunft. Transzendentale Dialektik). Yet this phenomenistic prejudice, having tenaciously survived many well grounded criticisms of the Kantian system (Cf. Livi, 1997) today has received new criticism and, in light of the ‘overcoming’ of the so-called ‘end of metaphysics’ (Cf. Ottonello, 2002) and in light of the contributions of analytical philosophy (Cf. Micheletti, 2002), can be considered untenable, precisely because the metaphysical approach of the ways of Aquinas have been recognized as valid, albeit with new and sophisticated interpretations concerning his point of departure and demonstrative method (Cf. Motta, 2002).

Yet, the re-affirmed possibility of a natural knowledge of the existence of God (above all as patrimony of common sense, and later as a metaphysical formalization), here has the meaning and value of an indispensable rational premise of faith, in terms of the condition of possibility for man’s understanding and acceptance of divine revelation, thus gaining access to supernatural knowledge. Such a re-affirmation does not imply a ‘rationalistic vision’ of the knowledge of God. Natural knowledge is, in fact, – as we have already shown – awareness of the unfathomable mystery of Transcendence, even acknowledging that this Mystery is the foundation of all reality; and supernatural knowledge is not presented as the definitive and complete unveiling of the divine nature, but rather the grace which allows us partial access to God’s intimacy, a vision ‘like in a mirror and in mystery’, and at the same time it is a prelude to further grace, to the promise of a ‘face-to-face’ encounter (the lumen gloriæ).
St. Paul, precisely in the passage of his Epistle containing these phrases, adds: « Now I know in an imperfect way, then I will know in a perfect way, just as I am known [by God] » (First Epistle to the Corinthians, 13:12). Faith’s knowledge is true knowledge, yet imperfect; with divine revelation, we know with certainty something of the intimate life of God, but that which we know (the Trinity of Persons in the unity of divine substance, the eternal plan of salvation of all men through the Incarnation of the Word) we cannot fully understand while we are in statu viæ.

In terms of this reality, the expressions of a classical author of mystical theology are very significant: « Who can investigate the sublime essence of God, ineffable and incomprehensible? Who can search his highest mysteries? Who will dare say anything about him who is the eternal existing principle of all created things? Who will boast of knowing the infinite God, who fills all with himself , encompasses all, transcends all, comprises all and escapes all? […] Let no one presume with investigating God’s incomprehensible mysteries: what, where and how he may be. These are ineffable, inscrutable, impenetrable mysteries.
« Believe one thing only, but with the strength of your whole heart: that God is always like this, as he has always been and will forever be. He is unchangeable. Who is God then? Father, Son and Holy Spirit are a single God. Do not desire to know anything else about God, […] Should any of you want to know what to believe, beware that you will not understand more by speaking than by believing. The more the knowledge of God becomes an object of discussion, the farther it seems to move away from us. Seek therefore the knowledge of God that stems not from wordy disputes, but from the sanctity of a good life. This knowledge springs from the simplicity of heart, not from putting together learned but impious opinions. If you pursue the Ineffable One with discussions, he will “go beyond you (Qo 7:23)” more than before. But if you seek him in faith, you will find wisdom at the city gates next to your home. You will see, albeit partly. But you will not be able to attain it, for it still is invisible and incomprehensible. God is invisible, and that is what we must believe, even though some knowledge can be had by those who have the gift of faith » (Abbot Columbanus, Instructions on Faith, 4-5; Works, Dublin, 1957, 65-66).

Contemporary theology gladly recognizes these dynamic aspects of grace in terms of the vision of God: « God did not reveal himself as a reality that our mind could encompass and possess. Discovering him never ends. […] His revelation attains its own coherence the moment when, coming close to it, we see that the revealed mystery is still largely hidden. Its partial revelation instils in us the passionate desire to know and understand always more » (Fisichella, 2002, 587). Therefore, a rigorous reflection on the faith in Revelation should not lead to any form of philosophical rationalism (and as a result, theological rationalism), nor should it lead to philosophical scepticism (which inevitably generates theological fideism) which today seems to reign: the conclusions of a philosophical analysis of the act of faith and of its object are to be understood through the prism of a delicate yet necessary gnoseological balance, which an already quoted theologian summarizes well with these words concerning man’s natural and supernatural of God: « He is not unknown or ignored by us, but rather the One who is incomprehensible » (Ibid.).
And yet, as one author has noticed, « Faith is not only communicable, but it is impossible not to communicate it, at least through that implicit communication of meaning which is given to one’s actions » (Zennaro, 2002, 45-46). Communication is born from the answer which is given to the imposing presence of the reality which surrounds man, which poses inescapable questions and to which Christianity offers a global answer of meaningfulness. In the first place, man examines the ‘relational’ context of the first encounter with the truth of Christ. Andrew and John, the two who ask Jesus the question: “Master, where do you live?”, are fully involved in their contemporary culture.