Science and Modernism

Because modern science has proven very effective at explaining the physical world, some have succumbed to the error of Modernism, which is not only harmful to religion but also actually harmful to the development of a true science which can more accurately explain nature.

The cognitional theoretical basis of Modernism is agnosticism, according to which human rational cognition is limited to the world of experience. Religion, according to this theory, develops from the principle of vital immanence (immanentism) that is, from the need for God which dwells in the human soul. The truths of religion are, according to the general progress of culture, caught up in a constant substantial development (evolutionism).

—Dr. Ludwig Ott's Fundamentals of Catholic Dogma pgs. 16-17

It appears that Modernism is only the subject of religion, the dogmas of which some may think the progress of modern science threatens. Yet it relates to science, too, since even though it is true that knowledge begins in the senses—i.e., from experience—it does not end there; rather, it ends in the intellect, the human's soul, in which exists the universal knowledge that science discovers. Agnosticism nihilistically states that it is futile "to know the reality corresponding to our ultimate scientific, philosophic, and religious ideas." (Shanahan 1908); one therefore cannot be agnostic and interpret quantum mechanics, for example, except possibly with the instrumentalist interpretation. Immanentism basically says that God and religion are manifestations of man, not realities apart from man and given to him by God, respectively; and evolutionism says man's nature changes. Although science has failed to prove any of these propositions, some assume them—consciously or not—in order to remove God from science and consequently also to ignore the study of God or theology, which is the noblest science of which the "Other sciences [e.g., the natural sciences] are called the handmaidens." (Summa Theologica Iª q. 1 a. 5 s. c.).

Before discussing how Modernism leads to pathological science, let us first give some historical context and see how Modernism affected the French Catholic physicist of the "Gibbs-Duhem Equation," Pierre Duhem (1861-1916), who, interestingly, thought that all fields of physics are reducible to thermodynamics.

2. Fideism or Rational Obedience

In the encyclical Pascendi Dominici Gregis of 1907, two years after Duhem's 'Physics of a Believer', the official position was made clear in the name of Pope Pius X. Of the dangerous aspects of the heresy it called "modernism" identified by the encyclical two concern me here, what it called the "agnosticism" of the modernists, and the separation of science and faith. The first for example was dangerous because of the damage it did to natural theology:

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. [...] Given these premises, all will readily perceive what becomes of Natural Theology, of the motives of credibility, of external revelation.

The second was under suspicion of fideism:

Having reached this point [...] we have sufficient material in hand to enable us to see the relations which Modernists establish between faith and science. [I]n the first place it is to be held that the object of the one is quite extraneous to and separate from the object of the other. For faith occupies itself solely with something which science declares to be unknowable for it. Hence each has a separate field assigned to it: science is entirely concerned with the reality of phenomena, into which faith does not enter at all; faith on the contrary concerns itself with the divine reality which is entirely unknown to science.

Pascendi goes on to suggest that the modernists really meant to subject faith to science but were afraid to say so, and was even to find pantheistic implications in the position. It can be assumed that one target of this passage was Alfred Loisy's attempt to separate the results of the critical analysis of Scripture from the dogmatic claims of the Catholic Church, and that another was the memory of late mediaeval and Renaissance theories of double truth, truth in philosophy separate from truth in faith; but the concern of the first passage to preserve the integrity of natural theology shows the importance of wider considerations. Duhem is not one of those identified as targets of the encyclical. Whether his work was even known to those who drafted it must be a matter of speculation. But quite apart from his explicit disapproval of the enterprise, it is hard to envisage the kind of natural theology that could be accommodated to Duhem's account of the aim and structure of physical theory.
The issue was basic, the subject even of dogmatic definition, by the First Vatican Council of 1870-71, the Council that, in non-Catholic circles at least, is more famous for the definition of Papal infallibility. That Council, using the double negatives usual in such definitions, had declared anathema anyone who should deny that the knowledge of God was accessible to human reason. Though what that meant is not easily determined, most of the bishops present must have meant to say that the knowledge of God was accessible to human demonstration, not of course that knowledge of Him contained in the creeds and dogmatic formulations of the Church, but the knowledge that there is a good God who created all things: the rest belonged to Revelation, not reason.
But whatever the bishops thought they were doing thus making the demonstrability of God's existence a matter of faith, the general strategy is clear enough: to offer the faithful what are technically known as motives of credibility, reasons that would make it rational to accept the Catholic faith and ecclesiastical authority. The faithful could be assured that, God's existence being demonstrable by reason, it was rational to accept the dogmatic formulations of the faith concerning Him offered by the church, and rational also to accept the authority of the Church that propagated this faith, rational to support the Church as it defended its temporal power against the new kings of a reunited Italy, and rational also to defend the Church in its resistance to the Prussian rulers of Germany and republican rulers of France. At the same time, of course, it turned Catholics into a disaffected element in all three states, a disaffected element the authorities had to disarm at the price of their own survival.
So it emerges that by propagating a system of physics that undermines natural theology Duhem has rendered himself suspect of the heresy (for that is the effect of the Council's decree) of fideism, the belief that the faith rests on faith and nothing else, and that conclusion was explicitly drawn by F. Mentré, one of those who wrote on Duhem's work after his death. In his eyes, Duhem's views were of no use on religion because of this fideist taint, connected with what he identified as its Pascalian sources, the subject of the next chapter. Furthermore, the counterpart of fideism is philosophical scepticism, the doubt about the reliability of knowledge of any kind, about its ultimate guarantees. Thus in 1893 Eugène Vicaire detected it Duhem's views "the poison of scepticism" and was appalled that such views should appear in a Catholic journal, the Revue des Questions Scientifiques, in which Duhem's early articles appeared.

3. The Revival of Scholasticism

But the consequences go even further, and it is here that neo-Scholasticism falls to be considered. There is no point in asserting the demonstrability of God's existence, or of anything else for that matter, unless there is available a philosophical system to do it in, just as to demonstrate God's non-existence a philosophical system, such as that provided by the various brands of positivism, was equally necessary. In 1878 the Encyclical Aeterni Patris of Leo XIII hit the nail on the head by citing St. Paul in favour of its view that 'false philosophy' was the source of the modern apostasy. The 'true philosophy' offered in its place was a revived Scholastic philosophy, the philosophy associated by the encyclical indiscriminately with Thomas Aquinas and the latter's thirteenth-century Franciscan contemporary Bonaventure, but in practice looking more to Aquinas as interpreted by such sixteenth-century commentators as Cajetan and Suarez.
The groundwork for the encyclical had been laid over the previous half-century. At least since the sixteenth century, there had always been a tendency towards Scholasticism in Catholic philosophy and theology, and corresponding difficulties with 'modern' philosophies. For example, an episode better known that some because of the attention Leibniz paid it, is the persecution of the followers of Descartes in the 1670s and 1680s because of the difficulties their philosophy created for the Eucharistic doctrine of transubstantiation defined by the sixteenth-century Council of Trent, the doctrine that at the words of consecration the substance of the bread and wine are transformed into the substance of the body and blood of Christ, leaving only the so-called accidents of colour, taste, and texture unchanged. Despite the intentions of the Fathers of the Council of Trent, this doctrine can hardly be understood outside the philosophy of substance and accident in which it is stated, still less if matter is defined, as it was by Descartes, as essentially, in substance that is, the space it occupies—and nobody suggested that that changed at the words of consecration!
Just as at the end of the nineteenth century Duhem was to turn the philosophy of positivism against the anti-religious conclusions of the positivists, so, in the early nineteenth century a serious of attempts was made, all of them resulting in condemnations for their authors, to adapt philosophies of non-Catholic origin, such as those of Kant and Schelling, for the purposes of Catholic apologetic. As interpreted by many, the problem seems to have lain in perceived violations of the balance between faith and reason demanded of Catholic orthodoxy: reason was to offer motives of credibility, to prepare the ground for faith by making credible the acceptance of a faith such as that revealed in the Scriptures and the decisions of the Councils of the Church, but not to go further. A group of Rome-based Jesuits, of whom the most prominent were Matteo Liberatore and Joseph Kleutgen, argued that only a scholastic philosophy, looking to that of Thomas Aquinas, would do, and they convinced Gioacchino Pecci, the future Pope Leo XIII, of the merits of their case.
In the Pope's mind the main object of the scholastic revival was theological, but there were at least two others: a revaluation of the thought of the Middle Ages, and of the Church's rôle in it, and indeed a re-affirmation of its value in the face of widespread denigration; and the thought that a revived Scholasticism, judiciously interpreted, might be found of use in questions of modern philosophy and science, despite prevalent expectations to the contrary. In short, by this action the Pope intended to re-affirm, against all the apparent odds, what he saw as the Church's heritage, and from that would no doubt flow improved morale among the troops confronted by a hostile world and, even, greater respect for the Church among those who did not belong to it.
The encyclical thus led to a theological programme to re-examine and restate Aquinas's 'five ways' for proving God's existence, to a historical programme to recover the mediaeval materials on which scholastic thought to contemporary questions, whether social, ethical, or scientific. These different programmes were not of course independent: the scholasticism available to the Pope had been mediated by the work of commentators at least two centuries distant from Aquinas's own time, so that a genuine revival of his thought had to go back past these to the sources, to find out what Aquinas had actually said; Aquinas's work was also apparently embedded in an obsolete natural philosophy, of generally Aristotelian character, so that if his theology was recoverable, it had in some way to be reconciled with later scientific ideas; and any application to contemporary questions had to depend on answers to the prior question of what the philosophy was that was to be applied.
The later progress of scholarship was in due course to call into question most of the answers initially given, but it is these initial answers that concern Duhem: the work of Aquinas was supposed to consist principally in the reconciliation of Christianity with Aristotle, and in the mid-twentieth century Dom David Knowles, a historian with a low opinion of the scholars of the century following Aquinas, was still presenting Aquinas's supposedly successful achievement of this goal as the crowning intellectual achievement of the Middle Ages. It was this Aristotelianism of Aquinas, and of scholastic philosophy as it was generally understood, that was perceived to be the main stumbling block in the way of a Scholastic revival, and it will be a main problem for the remainder of this essay. To the extent that Duhem was involved in neo-Scholasticism, if he was so involved, that involvement can be expected to show itself in Aristotelian themes in his work, and by a sympathetic treatment of mediaeval Aristotelianism, as well as by associations with journals with generally neo-Scholastic policies.

4. Duhem the Scholastic?

Given the obstacles to scholasticism mentioned in the previous paragraph, it is understandable that different would-be scholastics adopted different strategies to meet them. The Roman seminaries, for example, apparently maintained an integral Thomism with few compromises towards modern science, but this was hardly a serious option for a practising mathematical physicist interested in having his work taken seriously by his contemporaries. Another obvious possibility would have been to reject the whole thing root and branch, either outright, or in the manner of the Italian Agostino Gemmelli, who in 1904-05 proposed a Scholasticism that included modern thought. I believe that something like this was Duhem's final position, but it was, as will be seen, decisively rejected by Pope Pius X in his Encyclical Pascendi of 1907, and something will be said below about how Duhem got there: it is by no means obvious that outright rejection was his position when he wrote them, and his earlier reactions to Blondel seem to point the other way.
An obvious intermediate position was to try to adapt scholastic natural philosophy to make it conform to the discoveries of modern science, the position that seems to have suited the eirenic temperament of Désiré Mercier, the future Cardinal Archbishop of Malines, and his group at Louvain. This was the programme behind the Société Scientifique de Bruxelles, which Duhem seems to have joined as a lecturer at Lille, and he seems to have appreciated its attitudes and approaches enough to attempt to recruit Paul Tannery into its membership. Apart from its Annales, which published his Les Théories Électriques de J. Clerk Maxwell, its principal organ was the Revue des Questions Scientifiques, a heavyweight quarterly carrying in depth discussions of the scientific questions of the day, but intended for an educated lay audience. it was not afraid of carrying long multipart articles, and of these Duhem became a major contributor: it seems to have been his preferred place of publication for general philosophical and historical pieces throughout the 1890s. This was the journal that carried his 'Réflexions' of 1892, Vicair's critique, and Duhem's replies. One of the latter, not considered so far in this essay, seems as good a place as any to begin a consideration of Duhem's possible relation to neo-Scholasticism.
'Physique et Métaphysique' of 1893 was the first of Duhem's replies to Vicaire. It addressed the suggestion, made by more than one of Duhem's readers, that his rigourous separation of physics from metaphysics was no more than a cover for denigration of the latter: the metaphysician was free to get on with it in his corner while the Duhemian physicist got on with it in his without interference, the implication being the positivist one that physics was the only real knowledge to be had. Duhem insisted that this was not his intention. On the contrary, metaphysics was for him a genuine form of knowledge, indeed "more excellent" than physics, but separated from physics by having different objects and being governed by different methods. The Scholastic expertise with which he set out his views seems to have impressed not a few of his readers enough to make them wonder whether he had a scholastic mentor, for in the normal course of events this was not the sort of expertise a physicist could be expected to have. Be that as it may, Duhem was claiming to be classifying independent and legitimate science, not distinguishing sense from nonsense in the manner of earlier and later positivists.
Repeated in Duhem's later writings, this move has been the main source for the view that Duhem's prime philosophical inspiration was neo-Scholastic. But initially plausible as this interpretation may seem, it becomes less so when Duhem is compared with a genuine neo-Scholastic like Jacques Maritain, who did indeed distinguish his sciences, but only so that thereafter he could unite them, assign each of them its place in the overall system of the sciences, and say which sciences could and could not establish what on the foundations of which others. The basis for Maritain's scheme, as of numberless others of like provenance, is the view that some sciences can be subordinated, or sub-alternated, to others in the Aristotelian scheme of things. A science is conceived of as a deductive system of syllogisms, deduced from one or more definitions of the essences that are the subject matter of that science, and remaining within its genus or natural kind, and it is supposed that the conclusions of one science can serve as principles for another, as when the sciences of equilibria and music take their principles, as subaltern science, from the superior sciences of arithmetic and geometry. Famously, this scheme ran into difficulties with the applied mathematical sciences, such as astronomy in ancient times and terrestrial physics in modern: if Aristotle was right, natural philosophy should have been subordinate to 'physics', or, in Duhem's terminology, 'metaphysics', but the mathematical science of nature soon left Aristotelian metaphysics far behind, a point that will be considered further below.
I mention now two aspects of such schemes: they were only achieved at the price of distorting Aristotle, for whom mixed sciences would have meant mixing genera, something his methodological principles forbade; and their rationalistic atmosphere, not to say hubris, is remote indeed from a scientific world in which, as in the physics of Duhem, mathematical formulae are devised to meet the problems thrown up by experiment, not those suggested or deduced from a priori theory. The reconstruction of Aristotle that would reconcile his views to modern science would have to be pretty radical, radical both at the level of method and of content.
Nevertheless, there seems to have been one aspect of Aristotle's system that Duhem found somewhat promising: its freedom from a priori selection of the primary qualities by which, in the manner of the mechanical philosophy of the seventeenth century, all secondary qualities had to be explained. For him, what qualities were primary and what secondary ought to be a purely pragmatic matter, decided by the progress of theory and experiment as successive theories succeeded in classifying wider and wider collections of data. Where, though, he differed from Aristotle is that his physics was to be a mathematical science; it was to classify qualities, not explain them, and do so by replacing their measured intensities by symbols subject to mathematical manipulation; it was to be mathematical science whose form no metaphysical system could decide a priori: that form too was to emerge from the progress of physics, as successive theoretical classifications of the mathematical intensities of qualities, and the implied classifications of the qualities these represented, hopefully converged on the natural classification that was the goal of physics.
Such was the 'Aristotelianism' that Duhem advertised in a variety of articles in the middle to late 1890s, particularly in his historical works culminating in Le Mixte et la Cominaison Chimique and L'Évolution de la Mécanique, before repeating it yet again in 'Physicque de Croyant' after which it disappears from view. It was a pretty minimal Aristotelianism, but after 1905 even that disappears from view. To my knowledge, Duhem never withdrew such views, but their disappearance from his later writings is indicative of his final decisive rejection of neo-Scholasticism and all it stood for, of those of his earlier attitudes that had made it reasonable for Blondel in 1893 to tease him as a peripatetic. Duhem's ultimate reasons for this shift are not completely clear—some possible answers will be explored later in this chapter—yet there can be no question but that it came at a critical time, when the so-called modernist crisis was at its height, and neo-Scholasticism lay at the hearth of that crisis.
I have already referred more than once to the Encyclical Pascendi Dominici Gregris of 1907: the prominent rôle neo-Scholasticism played in it can hardly escape the notice of any reader; implicit in the doctrinal part, it becomes explicit in the disciplinary part that follows. We are told that a distaste for the scholastic method is the surest sign of modernism in any writer (What else would be expected of an adherent of a modern philosophy but opposition to scholasticism?), and the text goes on to insist that scholastic philosophy is henceforth to be the basis for Catholic thought:

We will and ordain that scholastic philosophy be made the basis of the sacred sciences. [...] And let it be clearly understood above all things that the scholastic philosophy We prescribe is that which the Angelic Doctor has bequeathed to us, and We, therefore, declare that all the ordinances of Our Predecessor on this subject continue fully in force [...] Further let Professors remember that they cannot set St. Thomas aside, especially in metaphysical questions, without grave detriment.

The Angelic Doctor is a Scholastic appellation for Thomas Aquinas.
From all this Duhem had largely stood apart, and events will show him moving yet further away from it. Even in his historical work to date, unusual for its time in that Aristotle is taken seriously, there is no trace of the work on mediaeval science that was to be expected of a historically-minded Catholic scientist in that environment, and was in the end to do more than anything else to perpetuate Duhem's fame. But, as will be seen, when he does get involved in mediaeval science, what he finds is not perhaps what the Pope had in mind. While Pascendi was insisting on the centrality of scholastic philosophy Duhem was increasingly associated with a journal committed to opposing that philosophy. The best place to illustrate Duhem's developing distance from neo-Scholasticism is his association with the Annales de Philosophie Chrétienne.

—R.N.D. Martin's Pierre Duhem pgs. 38-49 with quotes from Pope Pius X's encyclical Pascendi Domenici Gregis

Duhem, like Heisenberg, thought there was a "sharp division between faith and science." Even though Duhem made noble discoveries in the history of science related to mediaeval science's contributions, due in large part to the Catholic Church, to modern science; he refused to see the importance of adopting a Scholastic-Thomistic philosophy not especially for theology but for science. Why is this philosophy needed? Primarily because it opposes Modernism and sees that faith and reason "are like two wings on which the human spirit rises to the contemplation of truth (bina quasi pennæ videntur quibus veritatis ad contemplationem hominis attollitur animus):"

III. Relation Between Faith and Science

Faith and Science
Q.—Can we now have some idea of the relations which the Modernists establish between faith and science, including, under this latter term, history?
A.—'16. Having reached this point [...] we have sufficient material in hand to enable us to see the relations which Modernists establish between faith and science, including history also under the name of science.'
Q.—What difference do they make between the object of the one and of the other?
A.—'And in the first place it is to be held that the object of the one is quite extraneous to and separate from the object of the other. For faith occupies itself solely with something which science declares to be unknowable for it. Hence each has a separate field assigned to it: science is entirely concerned with the reality of phenomena, into which faith does not enter at all; faith on the contrary concerns itself with the divine reality which is entirely unknown to science.
Q.—Then, according to them, no conflict is possible between faith and science?
A.—'Thus the conclusion is reached that there can never be any dissension between faith and science, for if each keeps on its own ground they can never meet and therefore never be in contradiction.
Q.—'And if it be objected that in the visible world there are some things which appertain to faith, such as the human life of Christ'?
A.—'The Modernists reply by denying this.'
Q.—How can they deny it?
A.—They say: 'For though such things come within the category of phenomena, still in as far as they are lived by faith and in the way already described have been by faith transfigured and disfigured, they have been removed from the world of sense and translated to become material for the divine.
Q.—'Hence should it be further asked whether Christ has wrought real miracles, and made real prophecies, whether He rose truly from the dead and ascended into heaven,' what do they answer?
A.—'The answer of agnostic science will be in the negative.
'The answer of faith in the affirmative'
Q.—But is not that a flagrant contradiction between science and faith?
'There will not be, on that account, any conflict between them. For it will be denied by the philosopher as philosopher, speaking to philosophers and considering Christ only in His historical reality; and it will be affirmed by the speaker, speaking to believers and considering the life of Christ as lived again by the faith and in the faith.'
Q.—Faith and science acting thus in entirely separate fields, will there be, according to the Modernists, no subordination of the one to the other.
A.—'17. [...] it would be a great mistake to suppose that, given these theories, one is authorised to believe that faith and science are independent of one another. On the side of science the independence is indeed complete, but it is quite different with regard to faith, which is subject to science.'
Q.—Faith subject to science! But on what ground?
A.—'Not on one but on three grounds.'
Q.—According to the Modernists, what is the first ground?
A.—'For in the first place it must be observed that in every religious fact, when you take away the divine reality and the experience of it which the believer possesses, everything else, and especially the religious formulas of it, belongs to the sphere of phenomena and therefore falls under the control of science. Let the believer leave the world if he will, but so long as he remains in it he must continue, whether he like it or not, to be subject to the laws, the observation, the judgments of science and of history.'
Q.—What is the second ground of the subordination of faith to science?
A.—'Further, when it is said that God is the object of faith alone, the statement refers only to the divine reality not to the idea of God. The latter also is subject to science which while it philosophises in what is called the logical order soars also to the absolute and the ideal. It is therefore the right of philosophy and of science to form conclusions concerning the idea of God, to direct it in its evolution and to purify it of any extraneous elements which may become confused with it.'
Q.—What is the third ground?
A.—'Finally, man does not suffer a dualism to exist in him, and the believer therefore feels within him an impelling need so to harmonise faith with science, that it may never oppose the general conception which science sets forth concerning the universe.'
Q.—Then, according to the Modernist doctrine, faith is in bondage to science?
A.—Yes. 'It is evident that science is to be entirely independent of faith, while on the other hand, and notwithstanding that they are supposed to be strangers to each other, faith is made subject to science.'
Q.—How did Pius XI and Gregory IX stigmatize such doctrine?
A.—'All this [...] is in formal opposition with the teachings of Our Predecessor, Pius IX, where he lays it down that: "In matters of religion it is the duty of philosophy not to command but to serve, but not to prescribe what is to be believed but to embrace what is to be believed with reasonable obedience, not to scrutinise the depths of the mysteries of God but to venerate them devoutly and humbly."
'The Modernists completely invert the parts, and to them may be applied the words of another Predecessor of Ours, Gregory IX., addressed to some theologians of his time: "Some among you, inflated like bladders with the spirit of vanity strive by profane novelties to cross the boundaries fixed by the Fathers, twisting the sense of the heavenly pages . . .to the philosophical teaching of the rationals, not for the profit of their hearer but to make a show of science ... these, seduced by strange and eccentric doctrines, make the head of the tail and force the queen to serve the servant."'

IV. Practical Consequences

The Methods of Modernists
18. [...]
Q.—Is this ["the mutual separation of science and faith"] done also in other scientific work?
A.—'So, too, acting on the principle that science in no way depends upon faith, when they treat of philosophy, history, criticism, feeling no horror at treading in the footsteps of Luther [Prop. 29, condemned by Leo X, Bull, Exsurge Domine, May 16, 1520: 'It is permissible to us to invalidate the authority of Councils, freely to gainsay their acts, to judge of their decrees, and confidently to assert whatever seems to us to be true, whether it has been approved or reprobated by any Council whatsoever.'], they are wont to display a certain contempt for Catholic doctrines, or the Holy Fathers, for the Ecumenical Councils, for the ecclesiastical magisterium; and should they be rebuked for this, they complain that they are being deprived of their liberty.'
[...]

I. Rules Relative to Studies

The Study of Scholastic Philosophy
[...]
Q.—Would it be a great disadvantage to set aside St. Thomas?
A.—'Further let Professors remember that they cannot set St. Thomas aside, especially in metaphysical questions, without grave detriment.'
[...]
Q.—According to what law ought the study of natural sciences to be regulated?
A.—'47. With regard to profane studies suffice it to recall here what Our Predecessor has admirably said: "Apply yourselves energetically to the study of natural sciences: the brilliant discoveries and the bold and useful applications of them made in our times which have won such applause by our contemporaries will be an object of perpetual praise for those that come after us" (Leo XIII. Alloc., March 7, 1880). But this do without interfering with sacred studies, as Our Predecessor in these most grave words prescribed: "If you carefully search for the cause of those errors you will find that it lies in the fact that in these days when the natural sciences absorb so much study, the more severe and lofty studies have been proportionately neglected—some of them have almost passed into oblivion, some of them are pursued in a half-hearted or superficial way, and, sad to say, now that they are fallen from their old estate, they have been disfigured by perverse doctrines and monstrous errors" (loco cit.). We ordain, therefore, that the study of natural science in the seminaries be carried on under this law.'
[...]

Conclusion
The Church and Scientific Progress

Triennial Returns
'57. This, Venerable Brethren, is what we have thought it our duty to write to you for the salvation of all who believe. The adversaries of the Church will doubtless abuse what we have said to refurbish the old calumny by which we are traduced as the enemy of science and of the progress of humanity. In order to oppose a new answer to such accusations, which the history of the Christian religion refutes by never failing arguments, it is Our intention to establish and develop by every means in our power a special Institute in which, through the co-operation of those Catholics who are most eminent for their learning, the progress of science and other realms of knowledge may be promoted under the guidance and teaching of Catholic truth. God grant that we may happily realise our design with the ready assistance of all those who bear a sincere love for the Church of Christ. But of this we will speak on another occasion.
'58. Meanwhile, Venerable Brethren, fully confident in your zeal and work, we beseech for you with our whole heart and soul the abundance of heavenly light, so that in the midst of this great perturbation of men's minds from the insidious invasions of error from every side, you may see clearly what you ought to do and may perform the task with all your strength and courage. May Jesus Christ, the author and finisher of our faith, be with you by His power; and may the Immaculate Virgin, the destroyer of all heresies, be with you by her prayers and aid. And We, as a pledge of Our affection and of divine assistance in adversity, grant most affectionately and with all Our heart to you, your clergy and people the Apostolic Benediction.
'Given at St. Peter's, Rome, on the 8th day of September, 1907, the fifth year of our Pontificate.'

—Fr. John Fitzpatrick's Catechism of Modernism with quotes from Pope Pius X's encyclical Pascendi Domenici Gregis

Even though Pope St. Pius X says that one "cannot set St. Thomas aside [...] without grave detriment," he was primarily referring to the teaching and study of theology, and in section 47. appears to think the natural sciences should be regulated by a different set of rules and "without interfering with sacred studies." Yet in both cases he is stressing the importance of St. Thomas's "perennial philosophy" in order to avoid "perverse doctrines and monstrous errors" not only in sacred sciences but also in the "profane" or secular natural sciences as well. A notable example of a "perverse doctrine" or teaching in physics is the "many worlds" interpretation of quantum mechanics. In the solid "perennial philosophy," only one world can exist. (Summa Theologica Iª q. 47 a. 3).

The mathematician and philosopher Wolfgang Smith (author of "From Schrödinger's Cat to Thomistic Ontology" in The Thomist) calls Modernism's influence on science the "plague of scientistic belief:"

Yet, despite the fact of quantum indeterminism, not a few eminent scientists continue to champion the mechanistic tenet. Albert Einstein himself, as one knows, so far from admitting that the discoveries of quantum physics have overthrown the classical postulate, argued precisely in the opposite direction: it is the principle of determinism, he said in effect, that invalidates quantum mechanics as a fundamental theory. This illustrates quite clearly the philosophical and indeed a priori character of the tenet in question, and the fact that propositions of this kind can neither be verified nor falsified by empirical findings. This fact, however, remains generally unrecognized, with the result that the postulate of universal mechanism has retained to this day its status as a major article of scientistic belief.
My second example pertains to a more fundamental stratum of philosophical thought, and is consequently still more far-reaching in its implications: “physical reductionism,” let us call it (for reasons which will presently become clear). The thesis hinges upon an epistemological assumption, an idealist postulate, one could say, which affirms that the act of sense perception terminates, not in an external object as we commonly believe, but in a subjective representation of some kind. According to this view, the red apple which we perceive exists somehow in our mind or consciousness; it is a subjective image, a fantasy which mankind has all along mistaken for an external object. Thus thought René Descartes, to whom we owe the philosophical foundations of modern science. Descartes sought to correct what he took to be the mistaken notions of mankind concerning perceptible entities by distinguishing between the external object, which he termed res extensa, and its subjective representation existing in the mind or so-called res cogitans. What was previously conceived as a single object (and what in daily life is invariably regarded as such) has therefore become split in two; as Whitehead has put it: “Thus there would be two natures, one is the conjecture and the other is the dream.” It is to be noted that this Cartesian differentiation between the “conjecture” and the “dream” goes not only against the common intuitions of mankind, but is equally at odds with the great philosophical traditions, including especially the Thomistic, where the opposition becomes as it were diametrical. Now, it is this questionable Cartesian doctrine—which Whitehead refers to as “bifurcation”—that has served from the start as the fundamental plank of physics, or better said, of the scientistic world-view in terms of which we habitually interpret the results of physics. And once again we find that the two disparate factors—the operational facts of physics and their customary interpretation—have become in effect identified, which is to say that the tenet of bifurcation does indeed function as a scientistic belief.
I would like to emphasize that in addition to the fact that bifurcation contradicts the most basic human intuitions as well as the most venerable philosophical traditions, there is also not a shred of empirical evidence in support of this heterodox position. Nor can there be, as follows from the fact that physics can be perfectly well interpreted on a non-bifurcationist basis, as I have shown in a recent monograph. It turns out, moreover, that the moment one does interpret physics in non-bifurcationist terms, the so-called quantum paradoxes—which have prompted physicists to invent the most bizarre ontologies—vanish of their own accord. It seems that quantum physics has thus implicitly sided with the pre-Cartesian world-view.

—Wolfgang Smith's "The Plague of Scientistic Belief"

This mechanism has far-reaching philosophical consequences which in turn influence how subsequent science is performed and interpreted. E.g., in Galileo's description of tickling, he adopts a subjectivist, agnostic philosophy because he denies that the nature of "feather," something beyond the senses, can be known; for him, sense knowledge begins and ends in the senses.

I move my hand first over a marble statue and then over a living man. To the effect flowing from my hand, this is the same with regard to both objects and my hand [Here he assumes spatial motion is all that matters.]; it consists of the primary phenomena of motion and touch, for which we have no further names. But the live body which receives these operations feels different sensations according to the various places touched. When touched upon the soles of the feet, for example, or under the knee or armpit, it feels in addition to the common sensation of touch a sensation on which we have imposed a special name, "tickling." This sensation belongs to us and not to the hand. Anyone would make a serious error if he said that the hand, in addition to the properties of moving and touching, possessed another faculty of "tickling," as if tickling were a phenomenon that resided in the hand that tickled. A piece of paper or a feather drawn lightly over any part of our bodies performs intrinsically the same operations of moving and touching, but by touching the eye, the nose, or the upper lip it excites in us an almost intolerable titillation, even though elsewhere it is scarcely felt. This titillation belongs entirely to us and not to the feather [therefore subjectivism]; if the live and sensitive body were removed it would remain no more than a mere word. I believe that no more solid an existence belongs to many qualities which we have come to attribute to physical bodies-tastes, odors, colors, and many more.

—Galileo's Il Saggiatore pg. 275

As interesting as Gailileo's description of tickling may be, he is wrong. Here is why:

Those who hold for the subjectivity of sensible qualities maintain that such qualities have no existence independently of the sensing subject, and on this ground effectively deny the very existence of objective intentions for such qualities. They find convincing Galileo's example of the movement of a feather across the skin to explain the tickle. So they introduce a distinction between primary qualities such as movement and secondary qualities such as the sensed tickle, and hold that the primary qualities have objective existence whereas secondary qualities do not. As a result they populate the universe with particles in motion and attempt to explain all sensations by the various kinds of movement these particles undergo, meanwhile denuding the objective world of sensible qualities in their traditional understanding.
The source of the difficulty here is an improper grasp of the role of the mental representation in the knowledge act. To think of the concept as what is known, rather than seeing that the nature is what is known, though by means of the concept, is to cut oneself off from intellectual knowledge of the real, for one is always left wondering about any extra-mental reality to which the concept might correspond. Similarly, to think of the sensation or the percept as itself what is known, rather than seeing the sensible quality as what is known, though by means of the sensation or percept, is to be imprisoned within one's sense organs and brain. The result is a radical solipsism that prohibits individuals from ever making statements about the objects of experience, leaving them to dwell in a world of their own imaginings.
The tickle may be something sensed on the surface of the skin, but that admission surely does not permit the inference that there is no movement there, or extending the argument further to hold that there is no heat in boiling water, no color in a ruby or a rose, no sound in the cry of a bird, or no odor or taste in an onion. All of these are accidents or accidental modifications of the subjects in which they are sensed. Just as those subjects have natures (inorganic, plan or animal in kind), so accidents may be said to have natures in an analogous sense. And even if we cannot know precisely the nature of heat, of color, and so on, we can at least model those natures in terms of the modalities they introduce in the components of the substantial natures in which they exist, namely the electrons, atoms, and molecules [...]

—Fr. William A. Wallace, O.P.'s The Modeling of Nature (pgs. 148-149)

With the adoption of a Thomistic philosophy, we can avoid all these sorts of philosophical and scientific methodological errors; we can interpret quantum mechanics correctly, for example; and, in short, we can prevent scientistic belief from plaguing science.