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Pope St. Pius X

The following is Part VII in a series defending the claims of the Catholic Church. Read Part I here; Part II here; Part III here; Part IV here; Part V here; and Part VI here

(LifeSiteNews) — So far in this series I have given brief introductions to three of the classic proofs for the existence of God. Each of these three proofs begins from our awareness of the reality of causality and contingency in the world, of which we gain knowledge by means of our senses. The proofs argue from what we know of created things to the existence of an unmoved mover, an uncaused cause and a necessary being.  

They are, therefore, all arguments a posteriori of the kind explained in an earlier article in this series. We argue from the observed effects to the existence of the cause.

This kind of argument for God’s existence has been regarded as valid and compelling for more than two millennia, and by philosophers from a wide variety of cultures and religions.

However, over the past two hundred years their validity has been widely rejected by thinkers outside the Catholic Church, and even within the Church they have been questioned.

In this article, we take a temporary pause from discussing proofs for the existence of God and consider how the Catholic Church has responded to claims that the human intellect lacks the capacity to reach the knowledge of God’s existence through arguments a posteriori.

The influence of Immanuel Kant (1724-1804)

Immanuel Kant held that human reason is incapable of attaining certain knowledge of the nature of things beyond the range of the senses. He drew a distinction between the sensory phenomena, a thing’s appearances, which can be known, and what things are in themselves, which cannot be known. Under such a model we cannot argue from sensory phenomena to the existence of a being who cannot be known by the senses, and thus a posteriori proofs for the existence of God become impossible.

Kant’s influence over modern philosophy is so great, that, outside the Church, the traditional proofs for the existence of God have been dismissed without consideration for more than two centuries. It is simply assumed that reasoning of this kind cannot bring us certain knowledge about realities beyond the senses. 

As philosopher Celestine Bittle OFM writes:

Modern agnosticism is a philosophic theory which affirms the constitutional inability of the human mind to know reality, so that all investigation pertains merely to the ‘phenomenal.’ Behind the phenomena, most agnostics assert, is an absolute reality of some sort, but this reality is intrinsically unknowable. Kant divided the objects of knowledge into two general classes, ‘phenomena’ (appearances) and ‘things-in-themselves’; the former are all we know, the latter are inaccessibly hidden behind the phenomena and are absolutely unknowable. God is, therefore, unknowable, so far as human reason is concerned.[1]

Kant thought that while it was impossible for man to attain knowledge of God through the use of speculative reason, the existence of God must still be held as a “postulate of practical reason.” Kant held that belief in God was practically necessary for man if he was to rationally pursue his “highest good,” which Kant held to be a virtue united to happiness. 

As Bittle writes:

Thus, according to Kant, the existence of God, the freedom of the will, and the immortality of the human soul are indemonstrable, but belief in their truth is necessary for man so that he can intelligently perform his moral duties.[2]

Kant’s position regarding the existence of God is summarized in this way by Dominican theologian Reginald Garrigou-Lagrange:

Kant maintained that the speculative proofs for the existence of God are not convincing, that metaphysics is an impossibility, and that there are no other proofs for the existence of God except those of the practical or moral order, productive of moral faith, which is sufficiently certain, subjectively considered, but objectively considered is insufficient.[3]

By the early twentieth century, these key errors of Kant were forming the basis of a new heresy, which would be identified and condemned as Modernism. 

The heresy of Modernism and a posteriori proofs for the existence of God

On September 8, 1907, the feast of the Nativity of Our Lady, Pope St. Pius X offered a great gift to the Catholic world. His encyclical letter Pascendi Dominici Gregis condemned the new heresy of Modernism, and exposed the philosophical and theological errors which underpinned it.   

The following year the Italian Modernist Ernesto Buonaiuti published a “counter-encyclical” entitled The Programme of the Modernists. This document gained support from Modernists worldwide, including George Tyrrell in England.[4]

Buonaiuti, an admirer of the Protestant reformation, was committed to a radical “reform” of Catholicism from within the structures of the Church, and preferred to wait to be expelled rather than to voluntarily leave a Church whose doctrines he no longer believed.[5] He was shown extraordinary forbearance by the Church, but was finally excommunicated vitandus by Pope Pius XI in 1926.[6] 

In the Programme of the Modernists Buonaiuti defiantly rejected the traditional proofs for the existence of God. He stated:

Before all else, it is necessary to recognise that the arguments supplied by scholastic metaphysics to demonstrate the existence of God – arguments drawn from movement, from the nature of finite and contingent things, from the degrees of perfection and from the finality of the universe, – have lost all their value today. In the general revision which the post-kantian critique has made of the abstract and empirical sciences and of philosophical language, the concepts which serve as a basis for these arguments have lost the absolute character which the peripatetics of the Middle Ages had attributed to them. 

This bold affirmation vindicates the assertion of St. Pius X that the key error of the Modernists was their agnosticism. The previous year the pope had taught:

Modernists place the foundation of religious philosophy in that doctrine which is usually called Agnosticism. According to this teaching human reason is confined entirely within the field of phenomena, that is to say, to things that are perceptible to the senses, and in the manner in which they are perceptible; it has no right and no power to transgress these limits. Hence it is incapable of lifting itself up to God, and of recognizing His existence, even by means of visible things. From this it is inferred that God can never be the direct object of science, and that, as regards history, He must not be considered as an historical subject.[7]

St. Pius X continues:

Given these premises, all will readily perceive what becomes of Natural Theology, of the motives of credibility, of external revelation. The Modernists simply make away with them altogether; they include them in Intellectualism, which they call a ridiculous and long ago defunct system. Nor does the fact that the Church has formally condemned these portentous errors exercise the slightest restraint upon them.[8]

These errors had indeed, as St. Pius X states, already been infallibly condemned by the Vatican Council in 1870.

The teaching of the Vatican Council on the knowledge of God to be attained by natural reason

In its third session, on April 24, 1870, the Vatican Council infallibly taught the following about God:

The Holy, Catholic, Apostolic and Roman church believes and confesses that there is one true and living God, Creator and Lord of heaven and earth, almighty, eternal, immense, incomprehensible, infinite in intellect, in will, and in every perfection; who, being one, sole absolutely simple and immutable spiritual substance, is to be declared as really and essentially distinct from the world, of supreme beatitude in and by Himself, and ineffably exalted above all things which beside Himself, exist or are conceivable. 

In this definition the Council affirms God’s existence, defines the fundamental attributes of His divine nature, and absolutely excludes a pantheistic understanding of God. Canons followed in which atheism, materialism and pantheism were all anathematized. 

Atheism was condemned by the first canon:

If anyone denies the one true God, creator and lord of things visible and invisible: let him be anathema.

Materialism was condemned by the second canon:

If anyone is so bold as to assert that there exists nothing besides matter: let him be anathema.

The various forms of pantheism were condemned by the third and fourth canons:

If anyone says that the substance or essence of God and that of all things are one and the same: let him be anathema.

If anyone says that finite things, both corporal and spiritual, or at any rate, spiritual, emanated from the divine substance; or that the divine essence, by the manifestation and evolution of itself becomes all things or, finally, that God is a universal or indefinite being which by self determination establishes the totality of things distinct in genera, species and individuals: let him be anathema.

The final canon of this set anathematized those who deny that the world was created by God:

If anyone does not confess that the world and all things which are contained in it, both spiritual and material, were produced, according to their whole substance, out of nothing by God; or holds that God did not create by his will free from all necessity, but as necessarily as he necessarily loves himself; or denies that the world was created for the glory of God: let him be anathema.

The same session of the Council proceeded to define the role of human reason in attaining knowledge of God’s existence:

The same Holy Mother Church, holds and teaches that God, the beginning and end of all things, may be known for certain by the natural light of human reason, by means of created things, ‘for the invisible things of Him from the creation of the world are clearly seen, being understood from the things that are made’ (Rm 1.20); but that it pleased his wisdom and goodness to reveal Himself and the eternal decrees of His will to mankind by another, namely, the supernatural way.

In this definition the Church infallibly teaches that we may know of the existence of God by the use of our natural human reason. The contrary error is then formally condemned:

If anyone shall say that the one true God, our Creator and Lord, cannot be certainly known by the natural light of human reason through created things, let him be anathema.

The Council specified that that the certain knowledge which we attain of God’s existence is reached through reasoning from created things.

Thus, it is heretical to hold the position that the existence of God cannot be known with certainty by the human reasoning process, beginning from sense data obtained from created things. 

The Council made this definition because of the prevalence both of Traditionalism (a form of fideism discussed briefly in an earlier article) and the errors of post-Kantian philosophy discussed above.

A memorandum distributed to the fathers of the Council alongside the text of the schema, gave this explanation of its contents:

The definition that God can be certainly known by the light of natural reason, through the medium of created beings, as well as the canon corresponding to this definition, were deemed necessary, not only because of Traditionalism, but also because of the wide-spread error that the existence of God cannot be proved by any apodictic argument [an argument demonstrated with certainty], and consequently that by the no process of human reasoning can the certainty of it be established.[9]

Garrigou-Lagrange gives some other instructive illustrations of the Church’s mind on the capacity of the human intellect to reach certainty on the question of God’s existence.

In 1840 the Congregation of the Index required a writer suspected of fideism to assent to the following proposition:

[H]uman reasoning in and of itself is sufficient to prove with certainty the existence of God. Faith, being a supernatural gift, presupposes revelation, and hence cannot be consistently invoked to prove the existence of God against an atheist.[10]

The text here is alluding to the order outlined in the first instalment of this series, whereby the human intellect first recognizes God’s existence, then recognizes that God is capable of revealing Himself to mankind, then that the revelation has in fact been made manifest in Jesus Christ, and, finally, that it is authoritatively taught by the Church which He established. It is at this point that an act of supernatural faith is to be made.

In 1855 the same congregation made another writer agree to the following propositions:

[H]uman reasoning has the power to prove the existence of God with certainty, as well as the spirituality and liberty of the soul.[11]


[T]he method employed by St. Thomas, St. Bonaventure, and other Scholastics after them, does not lead to rationalism, nor can it be blamed for the fact that the contemporary philosophy of the schools drifted into Naturalism and Pantheism. Hence, no one has the right to reproach these doctors and teachers for having employed this method, especially as they did so with at least tacit approval of the Church.[12] 

The Vatican Council definitively dealt with the questions of fideism and pantheism as we have seen above.

But did the Council also exclude the errors of Kant?

Garrigou-Lagrange answers in the affirmative, noting that the Council specifies that human reason attains knowledge of God which is certain. Asserting that man must simply postulate that God exists in order to provide a basis for fulfilling moral duties, as Kant did, is not sufficient to avoid falling under the condemnation of the Council. The Council Fathers rejected six different amendments that would have removed this word “certain.”[13] 

Bishop Gasser, the official relator at the Vatican Council, placed the text of the Council in the following context during the debates:

You know, very Reverend Fathers, what opinion has become prevalent in the minds of many through the teaching of the French encyclopedists and the foremost defenders of the critical philosophy in Germany; this widely spread opinion is none other than that the existence of God cannot be proved with full certainty, and that the arguments which have at all times been so highly regarded, are still open to discussion. As a result, religion has been despised as if it had no foundation. 

Moreover, in these latter days attempts have been made in various places to separate morality from all religion; this is said to be necessary because of the fear that, when a man has reached a certain age and perceives that there is nothing certain in religion, not even the existence of God, he may become a moral pervert.[14]

This is the post-Kantian philosophy, which the Council Fathers sought to exclude by defining that the knowledge of God’s existence acquired by natural reason is certain. 

The Anti-Modernist Oath

Despite the clear teaching of the Vatican Council and the encyclical letter Pascendi, the Modernists continued to deny the validity of a posteriori demonstration of God’s existence, as seen in The Programme of the Modernists referenced above. 

Therefore, in order to prevent the spread of this, and other Modernist errors, among the clergy, Pope St. Pius X introduced the Anti-Modernist Oath on September 1, 1910.

This oath repeats the affirmations of the Vatican Council with a number of additions to make its doctrine even clearer. 

The oath begins:

I [name], firmly hold as true and accept everything which the infallible teaching authority of the Church has defined, maintained, and declared, especially those points of doctrine which are directly contrary to the errors of the present time. And first of all, I profess that God, the beginning and end of all things, can be known with certainty and therefore also demonstrated by the natural light of reason, through the things which He has made, that is to say, through the visible works of His creation, just as the cause is made known to us by its effects.

The Anti-Modernist Oath uses some additional words which are not found in the definitions of the Council. 

The Council taught that the existence of God can “be known with certainty by the natural light of human reason, by means of created things.”

The Anti-Modernist Oath on the other hand uses an expanded formulation: “can be known with certainty and therefore also demonstrated by the natural light of reason, through the things which He has made, that is to say, through the visible works of His creation, just as the cause is made known to us by its effects.”

In this way it amplifies and makes clear the meaning of the Council against the Modernist errors.

Visible works of creation

The Anti-Modernist Oath specifies that God is known “through the visible works of His Creation.” The use of the word “visible” in the oath more clearly excludes reliance on arguments from the demands of morality, such as that made by Kant. 

Garrigou-Lagrange explains:

The insertion of the word ‘visibilia,’ and this in italics, in the first proposition of the Antimodernist Oath, is a sign that the Church insists upon the literal interpretation of the words of the Council and of the quotation of St. Paul. To exclude sensible things from the phrase ‘e rebus creatis’ [by means of created things] and to say that the only certain proofs for the existence of God are those based upon the intellectual and moral life of man, would evidently be to depart from the plain and original meaning of the words.[15]

God’s existence can be demonstrated a posteriori

The Council definition used the words “can be known with certainty” whereas the Anti-Modernist Oath states: “can be known with certainty, and therefore also demonstrated.”

By this addition, the oath emphasises the meaning of the Council and makes clear that Catholics must accept that God’s existence can be demonstrated by rational argument from the things that have been made. 

The addition of the phrase “as the cause is made known to us by its effects” places it beyond the possibility of doubt that the text is speaking of demonstration a posteriori.

That human reason, on examining the things of creation, can reason to the existence of God is the clear teaching of both the Old and New Testaments.

In the book of Wisdom we read:

But all men are vain, in whom there is not the knowledge of God: and who by these good things that are seen, could not understand him that is, neither by attending to the works have acknowledged who was the workman:  But have imagined either the fire, or the wind, or the swift air, or the circle of the stars, or the great water, or the sun and moon, to be the gods that rule the world. 

With whose beauty, if they, being delighted, took them to be gods: let them know how much the Lord of them is more beautiful than they: for the first author of beauty made all those things. 

Or if they admired their power and their effects, let them understand by them, that he that made them, is mightier than they: For by the greatness of the beauty, and of the creature, the creator of them may be seen, so as to be known thereby. 

But yet as to these they are less to be blamed. For they perhaps err, seeking God, and desirous to find him. For being conversant among his works, they search: and they are persuaded that the things are good which are seen. But then again they are not to be pardoned. For if they were able to know so much as to make a judgment of the world: how did they not more easily find out the Lord thereof? (Wis 13:1-9)

And in the Epistle of St. Paul to the Romans:

For the wrath of God is revealed from heaven against all ungodliness and injustice of those men that detain the truth of God in injustice:  Because that which is known of God is manifest in them. For God hath manifested it unto them. 

For the invisible things of him, from the creation of the world, are clearly seen, being understood by the things that are made; his eternal power also, and divinity: so that they are inexcusable. 

Because that, when they knew God, they have not glorified him as God, or given thanks; but became vain in their thoughts, and their foolish heart was darkened. For professing themselves to be wise, they became fools. (Rm 1:18-22)

Both of these passages make it clear that the knowledge of God’s existence can be known with certainty from created things, and that a failure to recognize this is inexcusable. It also makes clear that this knowledge is open to all, and is expected of all, and not just philosophers or intellectuals.

Of course, not all men do in fact attain their first knowledge of God’s existence through these means. Many, for example, are taught about God by their parents, or receive knowledge of God from the teaching of the Church as they grow up.

Furthermore, neither the Council nor the oath mean to suggest that every person is able to follow all the steps of reasoning in a philosophical demonstration. As Garrigou-Lagrange says:

[The teaching of the Church] does not mean that scientific demonstration is accessible to all, but that reason, by a simple inference deduced from the principle of causality, immediately rises to the certainty that God exists.[16]

It is not necessary to understand all the complexities of an argument to recognize such simple truths as the need for a first uncaused cause, or the need for a divine governor who gives the world its directedness and order.

In fact, a person need not even see that the philosophical arguments work in order to humbly accept the Council’s definition and take the oath. 

Such a person can assent to the Church’s infallible teaching, while humbly recognizing the limits of their own intellectual capacity, which leaves them unable to perceive the validity of the demonstration.

As Garrigou-Lagrange states:

[T]hese same persons, if they possess supernatural faith, may by this faith give their assent… without perceiving that what is said is intrinsically true, just as they give their assent to the supernatural mysteries of the Trinity or of the Incarnation.[17]

Garrigou- Lagrange concludes his treatment of the Anti-Modernist Oath as it relates to demonstrations a posteriori with these words:

Now that the Church has adopted into her official language the precise term ‘demonstration,’ and added the phrase, ‘per visibilia,’ and especially ‘tamquam causam per effectus,’ she has shown without a doubt, that she officially adopts as her own the teaching of St. Thomas and of almost all other theologians on the natural means at our disposal for acquiring the knowledge of God and accepts as valid the proofs based on causality, which originate from the world of sense.[18]

To deny that the existence of God can be known with certainty, from the visible things of creation, as a cause from its effects, is heresy.

The Catholic Church upholds the capacity of man’s intellect to attain knowledge of God’s existence, from the things that have been made, by the natural light of reason.

This natural knowledge of God is the basis on which mankind can come to believe that God has delivered a revelation for our salvation. Natural knowledge of God is the foundation for supernatural faith. 


1 Celestine Bittle O.F.M, God and His Creatures, (Milwaukee, 1953), p40.
2 Bittle, God, p11.
3 Reginald Garrigou-Lagrange O.P., God: His Existence and His Nature, (trans. Dom Bede Rose, 5th edition, 1934), p 8-9.
4 Giacomo Losito, “Ernesto Buonaiuti and ‘Il programa dei modernisti’”, U.S. Catholic Historian, Vol. 25, No. 1, Winter, 2007), pp. 74.
5 Losito, p78.
6 This is the most severe form of excommunication, which completely separates a person from the Church. Buonaiuti died unrepentant and outside the Church in 1946, though many of his associates were to remain within the visible structures Church, continuing the programme of internal revolution.
7 St. Pius X, Pascendi Dominic Gregis, No. 6.
8 St Pius X, Pascendi, No. 6.
9 Garrigou-Lagrange, God, p7-8
10 Garrigou-Lagrange, God p8.
11, 12 Garrigou-Lagrange, God, p8.
13, 14 Garrigou-Lagrange, God, p9.
15 Garrigou-Lagrange, God, p17.
16 Garrigou-Lagrange, God, p22.
17 Garrigou-Lagrange, God,, p25.
18 Garrigou-Lagrange, God, p21