Category Archives: Epistemology

Gilson and “Critical Realism”

For the written essay, please click here

Etienne Gilson and the Critique of “Critical Realism”

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Etienne Gilson and the Relationship of the Realist Position with Idealism

(A joint effort by Benjamin Moser and Matthew Menking)

Étienne Gilson[1] was one of the best known Thomist philosophers of the 20th century.  He was born in Paris on 13 June 1884. He studied under many fine scholars, including Henri Bergson, and although he always maintained a respect for Bergson, his own thought was considerably different. When Gilson began to study medieval philosophy in depth, he saw strong connections with the thought of Descartes, including the use of many terms borrowed from scholastic thought, although modified in their meaning.


Ultimately, according to Gilson, the Cartesian experiment fails in its attempts to overcome skepticism and lead us to a certain knowledge of the real world. Instead, the method has produced almost nothing but skepticism, and the reactions to it have been the opposite extremes of pure empiricism or idealism.


Here we would like to offer a brief overview of Gilson’s criticisms of those contemporary realists who would like to do justice to the questions asked by the idealists and so set out using an idealist method to attempt to reach realist conclusions. We will then look at what Gilson says is the real answer to becoming a realist, which consists in making that realism a decision in the beginning.


Gilson’s General Criticisms of Other Approaches to Realism

                Gilson’s realism differed from a number of other approaches adopted by Thomists of his time.  Certain of these thinkers called themselves Critical Realists.  Their approach to the question of realism were varied.  Some, for instance, such as Cardinal Mercier adopted a “mediate” realism, inferring the existence of the external world in a manner similar to that of Descartes, while others, such as a Monsigneor L. Noel held to a so-called “immediate” realism, avoiding such inferences.

Gilson objected to critical realism.  To begin with, he was opposed to the very use of the term “critical” to distinguish these philosophies.  The term, in fact, had no clear, universal definition.  It was used at times simply to designate a refutation of skepticism, idealism or criticism – that is, a refutation which presupposes realism.  With this Gilson has no problems.  The term might also be used to distinguish a reflective, philosophical realism from naïve, common-sense realism.  While Gilson does not object to making this distinction, he thinks the use of such terminology as “critical realism” is unnecessary, for “at this rate all philosophy would be critical by definition, since all philosophy involves reflection.”[2]

If it is true that the mode of knowledge proper to common sense is infraphilosophic, naïve realism          cannot be elevated to the level of philosophy.  Therefore, there is no reason to use the expression,            as if it were necessary to distinguish, outside of philosophy, between realism that is naïve and one            that is not.  If it is naïve, realism is simply not philosophy; if it is philosophy, realism cannot be               naïve… We need not style ourselves critical realists for the simple fact that we are realists of the   reflective sort, which is the manner of philosophy itself.  So let us say that we hold a philosophical      realism and, since the problem only arises among philosophers, content ourselves with calling it                 realism, plain and simple.[3]

That is, if we are already engaged in philosophic discussion of realism then we are, by the definition under consideration, engaging in critical thought, and there is no reason to distinguish our position as anything more than realism.  To do so is redundant.  Furthermore, it “presents serious drawbacks.”[4]  For, if a “critical” in this case means something other than simply “philosophical,”  it will indicate a realism which is justified on idealist bases.  As Gilson says,

“If a realist…wants to use this term to signify that his realism is conscious of its foundations,        justified by reflection rather than the spontaneous judgment of common sense, either ‘critical         realism’ will simply mean ‘philosophical realism’ or else ‘critical’ will acquire a meaning distinct       from philosophical.’  In the latter case, experience shows and reason proves that it will become      necessary to justify realist conclusions with the help of an idealist method.”[5]

It is to this latter approach to realism – one that adopts an idealist method, the method of those very systems which it seeks to refute – that Gilson objects, and from which he distinguishes his own realism.

The systems to which realism is opposed all work within the paradigm set by Descartes: that one must begin with thought and, from that starting point only, reach things.

What do the systems which the neo-scholastic philosophers want to refute have in common? The          idea that philosophical reflection ought necessarily to go from thought to things. The        mathematician always proceeds from thought to being or things. Consequently, critical idealism            was born the day Descartes decided that the mathematical method must henceforth be the method             for metaphysics.[6]

Descartes himself, of course, tried to reach realist conclusions from his chosen starting point.  As this method was adopted by later thinkers, however, the very possibility of metaphysical realism was rejected.

That Descartes, although an idealist in method, was in intention a realist, is proved by his             Meditations on First Philosophy. We can also say that in asking himself under what conditions a          universal a priori mathematics is possible, he still left the door open for metaphysics as a genuine                 science. But when Kant carried the Cartesian method onto other ground and asked himself what    are the conditions which make Newtonian physics possible, he firmly shut the door on metaphysics                as a science, because all physics presupposes sensory intuition, which is plainly not to be found in                 the metaphysical ideas of the reason. Indeed, all idealism derives from Descartes, or from Kant, or         from both together, and whatever other distinguishing features a system may have, it is idealist to               the extent that, either in itself, or as far as we are concerned, it makes knowing the condition of being.[7]

This loss of the thing or being, Gilson maintains, is the necessary result of the idealist method.  For this reason he criticizes those attempts at realism which, in accordance with this method, attempt to reach being by beginning with thought.  To do so is impossible, he maintains, and those who engage in this endeavor are doomed to failure.

The Cartesian experiment was an admirable metaphysical enterprise bearing the stamp of sheer             genius. We owe it a great deal, even if it is only for having brilliantly proved that every           undertaking of this kind is condemned in advance to fail. However, it is the extreme of naivety to               begin it all over again in the hope of obtaining the opposite results to those which it has always         given, because it is of its nature to give them.[8]

If one begins with thought, rather than with the real being of external things, he has already trapped oneself inside thought.  “He who begins with Descartes,” says Gilson, “cannot avoid ending up with Berkeley or with Kant”[9]

The illusion, which people who make attempts of this kind suffer from, even when they struggle             hardest against it, is that one can extract an ontology from an epistemology, and, by this or that                method, discover in thought anything apart from thought. A something outside thought cannot be thought of. There could be no better formula to describe idealism. And by it idealism stands condemned, because philosophy can no more do without what is not thought (or things) than it can            do without thought itself, and if one cannot get outside oneselfto arrive at things when one makes             thought the starting point, that proves that thought is not the point one should have started from.[10]

History bears witness to the inevitable results of the idealist method.  We see not only the failure of Descartes, and the results of idealists like Kant and Barkeley, but the failure of those realists who have adopted their method.  Not that Gilson considers an historical analysis able to demonstrate the necessary impossibility of a critical realism.  “Such an approach is necessary yet insufficient, for the fact that ten, twenty or a hundred philosophers have failed to find the solution to a problem does not prove that the problem is impossible to solve.”[11]  None the less, it is telling that thinker after thinker has failed to solve the problem.  Furthermore, in the face of this, the burden of proof lies upon the critical realists.

Each time we have discussed some particular form of critical realism and found it lacking, others               have always claimed that another form of critical realism might overcome our objections.  And if        we then demonstrated the insufficiency of the next form of critical realism, still another was trotted              out.  The partisans of critical realism maintain that this process must continue until it has been            proven that their position is impossible as a matter of principle.  To this we reply that, if those who      maintain that critical realism is possible in principle never provide a factual demonstration, it is a     bit much for them to demand that their adversaries accept this doctrine on the strength of the                 promise of future proofs.  It is up to them to show that it is indeed possible… While waiting,       however, we may occupy our time profitably by demonstrating the inherent self-contradiction      involved in each critical realism which has been advanced up to now and inquiring whether this     self-contradiction is not coessential with the very question asked.[12]



Gilson’s Criticism of Some Particular Such Approaches

In light of the above considerations, let us consider some of the attempts at critical realism with which Gilson dealt. Gilson tells us clearly, and repeats it often, that “every refutation of an error founded upon the consequences of that very error must inevitably fall back into that same error from whose consequences it took its starting point.”[13] Some attempts at a “critique of the critique” are undertaken by well-intended neo-scholastic authors, but all seem to fail because of the premises they accepted from the idealist method they intended to refute. This is because “whoever sticks a finger into the machinery of the Cartesian method must expect to be dragged along its whole course.”[14]


One such well-intended realist is Cardinal Mercier. He posits the method of a “mediate realism” and attempts to justify the real object of sensible forms through the principle of causality. What the cardinal wishes to do, one thinks, is to take Descartes method and avoid ending up with the result of Berkley. In basic form, he wishes to show that the contingency of the impressions of objects on the senses prove that they are objectively “out there,” since it is not we who act on ourselves. “Either I am the cause of my sensations, or something other than myself is.”[15] We easily understand that they are not of our own making.


The problem is, many other solutions “save the appearances,” to say the least. Not only Berkley’s idealism, but the occasionalism of Malebranche, the parallelism of Spinoza, or the “pre-established harmony” of Leibniz all explain the data. These positions all imply that the contingent, “non-selfed” sensations are given from the mind of God (or a similar method) and not from an objective reality “out there.” It becomes quickly apparent that the principle of causality, merged to the contingent nature of those “things” which cause sensation, cannot be a legitimate proof of the objectivity of a material world. At best, a material world is merely one possible explanation of the data. We are forced to concede that a mediate realism is no realism at all, as it can in no way posit a direct knowledge of the things-in-themselves, not even being able to prove that there are indeed things-in-themselves.


Gilson then looks at the question of whether a realism can be both critical and immediate at the same time. This is viewed under the research of Monsignor Noel, whose thought on the work of Cardinal Mercier gives rise to some confusion in Gilson.[16] Noel claims to be in general agreement with Mercier, and Gilson gives some valid criticism to this claim. As far as Etienne Gilson is concerned, however, this disagreement of Gilson with Noel’s assessment of Mercier’s position has no adverse effect on consideration of Noel’s position in itself. The best explanation for some of Noel’s alleged agreement with the Cardinal’s work is that the monsignor is able to “read into” the Cardinal’s work his own, due to some ambiguities.


The term immediate realism holds that the mind is able to grasp immediately “a reality independent both of the thoughts which it represents and of the act of thought that apprehends it.”[17] But what do we make if the “critical” label here? The critical method seems to require an indisputable certainty. This would imply that some critical starting point precedes the philosophy in question. But if this is so, then that starting point holds itself superior to realism, for it is a starting point that holds epistemology as superior to metaphysics. If “being” is not first, it cannot become first after a prior principle. This is simply absurd, and realism demands that being is first. Realism, then, will always start with metaphysics as the judge of all other sciences, since it deals with first principles.


Realism, likewise, starts with the fact of the existence of the things-in-themselves. “As soon as one accepts the idea of immediate realism, there can, by definition, no longer be a question of the existence of the outside world.”[18] What, then, is the problem with this so called immediate realism? Noel does not really go straight to the real, to reality. He posits an apprehended reality, and then starts from the point of “the apprehended.” In other words, this immediate realism “is planning…to consider in the ‘apprehended’ real only the ‘apprehended’ without the reality.”[19]


What has happened here is a repetition of former problems. We have once again cut ourselves off from reality (only this time at a slightly varied point) and then begin to seek a way back. “Put in the simplest terms, the question comes down to what has been called ‘the problem of the bridge’.”[20] We keep isolating thought from things, or rather, knowledge from things, as if they were two spatially separated objects, and then seeking a way to reunite then, come up short.


Any time we make some such division, we start from the point of view of the idealist. Here, it is worth repeating: “every refutation of an error founded upon the consequences of that very error must inevitably fall back into that same error from whose consequences it took its starting point.”[21] Each cutting off of the knowledge of the thing known from the thing known will create an unbridgeable divide. The idealist, knowingly or not, always has an advantage in the discussion if we miss this. “All idealist objections to the realist position are formulated in idealist terms. So it is hardly surprising that the idealist always wins. His questions invariably imply an idealist solution to problems.”[22]


Like most false philosophies, there is a great coherence, even brilliance, in the system. It all holds together quite nicely as long as we accept just one little absurdity in the beginning. “One is mistaken in trying to refute it [idealist systems] by accusing it of not being logical enough. On the contrary, it is a doctrine that lives by logic, and only logic, because in it the order and connection of ideas replaces the order and connection between things.”[23] One would do well here to turn to ‘Godel’s theorem’ and reflect on its possible implications here.


Gilson provides an evaluation of a few other neo-scholastic authors. One author is Fr. Picard,[24] whom Gilson spends considerable time evaluating in his Thomist Realism, although he does not seem to take Fr. Picard’s arguments to be on the same level as those of Cardinal Mercier or Monsignor Noel. With each “critical realist” that Gilson evaluates the details differ, but it is the same conclusion that is drawn. One either starts as an idealist or as a realist. If a person thinks he can make this choice after a critical evaluation of the theory of knowledge, he has actually made the choice to be an idealist in the very act of this decision. This is a choice that is made in the beginning. We now turn to why one would make such a choice.


Gilson’s Own Methodical Realism

In Etienne Gilson’s A Handbook for Beginning Realists,[25]Gilson offers thirty points of reflection, each in the form of a single paragraph. We shall take a look here at the first in some depth, using points from the others to deepen our understanding.

“The first step on the realist path is to recognize that one has always been a realist; the second is to recognize that, however hard one tries to think differently, one will never manage to; the third is to realize that those who claim they think differently, think as realists as soon as they forget to act the part. If one then asks oneself why, one’s conversion to realism is all but complete.”[26]

1.   The first step on the realist path is to recognize that one has always been a realist.


Reaslism is, of course, the default position, the common sense position. Now one may reply that the philosopher is one who overcomes common sense. But this is not accurate. Rather, the philosopher is one who develops and forms what he knows, perfecting the use of common sense. The fact that realism is the common sense position is not an argument for one to accept a naïve common sense, but rather, to demonstrate the right use of the senses and the intellect in knowledge of the real world as they are.

Commonly, arguments are made against realism on the basis of a mistrust of the senses. One such argument is that, when dreaming, we do think we are knowing a real world around us, and yet this is not the case. From here, it is “proved” that our thinking we are reaching the real world “out there” with our thought is not realiable. “A man who is dreaming feels no different from a man who is awake, but anyone who is awake knows he is altogether different from someone who is dreaming.”[27]


Another similar argument is that of illusions. But we see again that it is on the side of idealism, not realism, that the trouble is unanswerable. The fact that there are visual (and other) illusions proves all our perceptions are not illusions. “The idealist only finds these illusions so upsetting because he does not know how to prove they are illusions. The realist has no reason to be upset by them, since for him they really are illusions.”[28]


2.   The second is to recognize that, however hard one tries to think differently, one will never manage to.

When Descartes wrote his Meditations, it certainly gave man something to think about, even if he was in no way the first to ponder such questions.[29] But even Descartes showed, as we have mentioned above, that he was “in intention a realist.”[30] Even he seemed to realize that his  awareness of himself as thinking thing was preceded by his knowledge of himself as a thinking thing. For the “greatest difference between the realist and the idealist is that the idealist thinks, whereas the realist knows…The idealist, however, because he goes from thought to things, cannot know whether what he starts from corresponds with an object or not.”[31] Do we not ask, if told by someone that “they are thinking” ask the automatic question: “thinking about what?”


3.   The third is to realize that those who claim they think differently, think as realists as soon as they forget to act the part.


Many of these idealist intellectuals have developed extensive and logically coherent systems in the manner of their dialogue and of their literary output. But when it comes to the actual living of ordinary life, simple conversations with them will almost always reveal a realist assumption, even if subconscious.  This is something that many would not even deny. Renee Descartes and David Hume would each tell you that you should live, not as a skeptic, but through your common sense reasoning. Descartes skepticism obviously derived from his subjectivism and idealism. Hume, a professed empiricist, showed many tendencies, however, of the rationalist in his skeptical thought. Both thinkers, however, acted upon their realist assumptions in their day to day activities whenever they were not actively contemplating their “new worlds.”


4.   If one then asks oneself why, one’s conversion to realism is all but complete.


Rather than being enlightened by a new vision of the truth, as an idealist might claim about their idealism, the idealist in reality has to keep convincing himself of the truth of his system. He must continually adjust the reality around him to fit into the mold of his preconceived system.


The realist, however, simply updates his “total experience” of reality and modifies his thought according to that reality. Rather than spending his efforts in “modifying” reality, he grows in understanding of that reality. When one tires of the fight to create his world and ponders simply living in it, he is all but a realist.


Concluding Thoughts

In discussing the possibility of escape from subjectivism, our author Gallagher stated that “Once we recognize that there is no problem of getting outside of consciousness, we have recovered an essential vantage-point.  To be conscious is already to be outside oneself.  We do not have to break through the container of consciousness, because consciousness is not a container.”[32]  One ought not to begin inside thought and try to find a way out, for that very starting point is an error.  One need not escape from subjectivism from within it, but need only avoid its false foundation.

This is similar to the position of Gilson.  If one is to be a realist, one must begin with realism.  He must begin with the self-evident real being of external things.  Not that his realism is naïve common-sense realism, for it is reflective and conscious of its own foundations.  But, there is no need to enter into the Cartesian endeavor of demonstrating their being, for their being is the starting point of our thought – it is the first thing we know, without which is no consciousness.  If we try walking down that road, we will never reach our desired destination.  If one is to be a realist, he must recognize that there is no bridge one needs to cross from thought to thing, and that if one employs the idealist, critical method he will never be able to build such a bridge.  In his words, “there is no middle ground.  You must either begin as a realist with being, in which case you will have knowledge of being, or begin as a critical idealist with knowledge, in which case you will never come in contact with being.”[33]  Being is the only sound starting point for philosophy.

While the last few centuries have seen the method of idealism tried and modified in so many ways in a critical attempt to secure our knowledge, the rapidly changing systems ought to tell us something of the instability of this project. True, “most of our contemporaries think that, at bottom, being a philosopher and adopting an idealist method are one and the same thing.”[34] But as philosophy is the love of wisdom, we must ask if our philosophy is bringing us an understanding of reality. Is that not its purpose? The realist needs to be careful to always let the world around him shape his understanding of that world, modifying his understanding as he grows. But at least the realist system places this demand on the philosopher.


While the study of philosophy itself is certainly important, in the end, we ought to be studying things, so as to have greater knowledge. “When an idealist genuinely thinks as an idealist, he perfectly embodies the essence of the ‘professor of philosophy’, whereas the realist, when he genuinely thinks as a realist, conforms himself to the authentic essence of a philosopher; for a philosopher talks about things, while a professor of philosophy talks about philosophy.”[35] These are certainly powerful words, spoken by a professor of philosophy, one of the greatest historians of philosophy of the last century, and all the while a true realist; a man of great wisdom.




A short biography of Etienne Gilson by Jon Cameron of the University of Aberdeen


Étienne Henri Gilson was born into a Roman Catholic family in Paris on 13 June 1884. He was educated at a number of Roman Catholic schools in Paris before attending lycée Henri IV in 1902, where he studied philosophy. Two years later he enrolled at the Sorbonne, graduating in 1907 after having studied under many fine scholars, including Lucien Lévy Bruhl, Henri Bergson and Emile Durkheim.


Gilson taught in a number of high schools after his graduation and worked on a doctoral thesis on Descartes, which he successfully completed (Sorbonne) in 1913. On the strength of advice from his teacher, Lévy Bruhl, he began to study medieval philosophy in great depth, coming to see Descartes as having strong connections with medieval philosophy, although often finding more merit in the medieval works he saw as connected than in Descartes himself. He was later to be highly esteemed for his work in medieval philosophy and has been described as something of a saviour to the field.


From 1913 to 1914 Gilson taught at the University of Lille. His academic career was postponed during the First World War while he took up military service. During his time in the army he served as second lieutenant in a machine-gun regiment and was awarded the Croix de Guerre for bravery upon relief from his duties. After the war, he returned to academic life at Lille and (also) Strasbourg, and in 1921 he took up an appointment at the Sorbonne teaching the history of medieval philosophy. He remained at the Sorbonne for eleven years prior to becoming Professor of Medieval Philosophy at the College de France in 1932. During his Sorbonne years and throughout his continuing career Gilson had the opportunity to travel extensively to North America, where he became highly influential as a historian and medievalist, demonstrating a number of previously undetermined important differences among the period’s greatest figures.


Gilson’s Gifford Lectures, delivered at Aberdeen in 1931 and 1932, titled ‘The Spirit of Medieval Philosophy’, were published in his native language (L’espirit de la philosophie medieval, 1932) before being translated into English in 1936. Gilson believed that a defining feature of medieval philosophy was that it operated within a framework endorsing a conviction to the existence of God, with a complete acceptance that Christian revelation enabled the refinement of meticulous reason. In this regard he described medieval philosophy as particularly ‘Christian’ philosophy.


Gilson married in 1908 and the union produced three children, two daughters and one son. Sadly, his wife died of leukaemia in late 1949. In 1951 he relinquished his chair at the College de France in order to attend to responsibilities he had at the Institute of Medieval Studies in Toronto, Canada, an institute he had been invited to establish in 1929. Gilson died 19 September 1978 at the age of ninety-four.


His works include: La liberté chez Descartes et la théologie (1913); Le Thomisme (1919, trans. 1924); Etudes de philosophie médiévale (1921); Saint Thomas d’Aquin (1925); Introduction a l’etude de S. Augustin (1929; trans. 1960); L’espirit de la philosophie medieval (2 vol., 1932; trans. 1936); La théologie mystique de Saint Bernard (1934; trans. 1940) Christianisme et philosophie (1936); The Unity of Philosophical Experience (1937); Réalisme thomiste et critique de la connaissance (1939); God and Philosophy (1941); L’Etre et l’essence (1948; trans. 1949); La philosophie de saint Bonaventure (1953; trans. 1965); Christian Philosophy in the Middle Ages (1955); Painting and Reality (1957); Elements of Christian Philosophy (1960); Le philosophe et la théologie (1960; trans. 1962).

[1]  See the Appendix at the end of this paper for a short bibliography by Jon Cameron of the University of Aberdeen

[2] Gilson, Thomist Realism and the Critique of Knowledge, tr. Mark A. Wauck, (San Francisco: Ignatius Press, 1986) 51.

[3] Ibid., 51-52.

[4] Ibid., 52.

[5] Ibid., 52.

[6] Gilson, Etienne (2011-10-12). Methodical Realism (Kindle Locations 32-35). Ignatius Press. Kindle Edition.

[7] Ibid., Kindle Locations 44-46.

[8] Ibid., Kindle Locations 95-97.

[9] Ibid., Kindle Locations 89-90.

[10] Ibid., Kindle Locations 160-161).

[11] Thomist Realism, 149.

[12] Ibid.,  153.

[13]  Gilson, Thomist Realism, 46

[14]  Ibid, 48

[15]  Gilson, Methodical Realism, 30

[16]  See Methodical Realism, 47-50

[17]  Ibid, 55

[18]  Methodical Realism, 48

[19]  Ibid, 49

[20]  Ibid, 13

[21]  Gilson, Thomist Realism, 46

[22]  Gilson, Methodical Realism, 93

[23]  Ibid, 99

[24]  See Thomist Realism, 87ff

[25]  This “handbook” is Chapter V in Gilson, Methodical Realism

[26]  Methodical Realism, 93

[27]  Ibid, 101

[28]  Ibid, 102

[29]  E.g., Augustine made a similar use of doubt as a tool for the refutation of skepticism.

[30]  Gilson, Methodical Realism, 12

[31]  Ibid, 94

[32] Kenneth T. Ghallagher, The Philosophy of Knowledge, (New York: Sheed and Ward, 1964), 47.

[33] Thomist Realism, 149.

[34]   Ibid, 79

[35]   Ibid, 95


The following works will be consulted for my Epistemology project in PHL 620: Epistemology at Holy Apostles College and Seminary on “Realist Premises for a Realist Conclusion.”  The project will explore the history of attempts to come to a realist worldview using the premises of the critical method, and the failures to do so.

Gallagher, Kenneth T. The Philosophy of Knowledge. New York: Sheen and Ward, 1964. This work provides general background and historical information on the topic of epistemology and the various positions under which it has been viewed.

Gilson, Etienne. Methodical Realism: A Handbook for Beginning Realists. San Francisco, CA: Ignatius Press, 2011. This work lays out in a clear way what it speaks of in the title. After several essays on the difficulties encountered by Thomists in their dealings with modern and contemporary epistemology, it lays out an outline, almost of meditations, on which one can build a strong foundation for a realist view of knowledge and of the real world.

Gilson, Etienne. Thomistic Realism and the Critique of Knowledge. San Francisco, CA: Ignatius Press, 1986. In this work, Gilson analyzes several attempts of realist philosophers to show the truth of the realist position while engaging the adherents of the critical method at their own level; he shows why this ultimately must fail.

Gilson, Etienne. The Unity of Philosophical Experience. San Francisco, CA: Ignatius Press, 1999. This work shows, by historical survey, the unity of the project of attempts at human knowledge. It shows how in each case that turns away from realism, realism is again sought, for it is at minimum the default position of the human intellect.

Wallace, William A. The Elements of Philosophy: A Compendium for Philosophers and Theologians. Washington, D.C.: Catholic University of America Press, 1977. This work provides a general but densely packed overview of the discipline of Epistemology from a Thomistic Realist perspective, as well as being a useful reference for related fields, especially metaphysics and the history of philosophy.