I. Introduction*

St. Thomas of Aquino was born in the early 13th century to a high noble family that counted as its relatives two Holy Roman Emperors and the kings of Aragon, Castile, and France. Despite his heritage, St. Thomas chose the life of a teacher in the Dominican mendicant (begging) order instead of the high ecclesiastical office planned by his family, whose members even detained him for more than a year to try to change his mind. (In later life he would also turn down an archbishopric to continue his teaching work.) Living in an age when political loyalties and cultural differences were transcended by a common Faith and language of scholarship, St. Thomas would work in France, Germany, and Italy until before his death around the age of 49.

The 13th century was, in many ways, the golden age of Scholasticism, the Christian intellectual movement that emerged with the Latin Renaissance of the 12th century and found its home in the universities of Western Christendom. It was characterized by its rigorous use of logic and dialectic to apply the Christian Faith, which led to the rise of many schools of theology, philosophy and law within the doctrinal framework of Catholic Christianity. In St. Thomas’ time, Latin thought had recently encountered the metaphysical and ethical writings of Aristotle, and in the ensuing debates with extreme Aristotelians and the anti-Aristotelians alike, St. Thomas would prove a formidable controversialist and speculative thinker. It is largely due to him that the Aristotelian corpus was purified of its errors and integrated into Catholic thought.

St. Thomas’ writings were marked by his openness to all the intellectual traditions known in his time. Thus his theological works contain, alongside copious reverent citations of Sacred Scripture, references to the Greek philosophical tradition (including its Roman, Jewish and Muslim interpreters); the theologies of the Church Fathers, especially St. Augustine (whose writings, like the Scriptures of St. Paul and St. John, were influenced to varying degrees by Greek philosophy); Roman law as revived by the Latin canonists; and the writings of earlier Scholastics, particularly St. Anselm and Peter Lombard. Using the dialectical method of Peter Abelard and the categories of Aristotelian logic, St. Thomas sifted these traditions for their valid insights, which he melded into a comprehensive Christian synthesis.

For St. Thomas was, above all, a Christian theologian, and so the integrating principles of his thought were founded on his devout Catholic Faith. He affirmed that God is the source of all truth[1], including what we know through philosophy (rational inquiry on God’s creation) and sacred doctrine (divine revelation, which reason receives through God-given faith)[2]. Of these two, sacred doctrine is nobler because it communicates the truths of salvation, which are beyond the reach of reason[3]; and because, being God’s utterance, it gives greater certainty even on truths within reason’s grasp[4]. In sum, St. Thomas was confident that philosophy rightly conducted cannot contradict sacred doctrine rightly understood[5], which completes and corrects it[6]; and he sought to demonstrate the harmony of faith and reason throughout his work.

But while we need to believe in truth for our beatitude[7]–since we cannot love God if we don’t know Him–it is charity (supernatural love of God) that unites us to Him[8]. Because our capacity for love is limited by our nature and weakened by sin[9], God gave us His only-begotten Son Jesus Christ to be our Savior and Lord[10]. By His Passion Christ redeemed us from sin, as His members in His mystical body the Church[11], and reconciled us with God[12]; and by the grace we receive in the sacraments of His Church, which derive their power from the Passion of Christ[13], God elevates our nature that we might share His divine life and do His commandments[14]. Thus are we able to supernaturally love God and our neighbor, and to see Him face to face in eternal beatitude[15]. In short, as the synthesis of St. Thomas is founded on the unity of God’s truth, so it is consummated in the communion of His love.

The outline and method of St. Thomas’ thought can be clearly seen in his most famous work, called the Summa Theologica (Summation of Theology). Subdivided into parts, questions, and articles, its general structure begins with God and returns to Him (following the exitus-redditus schema of Christian Neoplatonism, according to many analysts). As legions of students have seen from the much-anthologized article “Whether God exists?”, each article begins by stating the Objections to the correct conclusion. Then Aquinas cites an authority for his position (“On the contrary…”), followed by a reasoned argument for its correctness (“I answer that…). The article then concludes with Replies to the Objections. Each question and article builds on the conclusions of preceding questions, and article, making the Summa a theological edifice systematically built brick by brick from the best of Christian and non-Christian thought.

The impact of St. Thomas’ achievement in Catholic Christian thought cannot be over-stated. In the 16th century, his theology of grace (which united the moral emphasis of the Western Fathers and the mystical focus of the Eastern Fathers) was used by the Council of Trent to define the Catholic doctrine of salvation, and allowed the Church to steer clear of both Protestant dualism and Eastern Orthodox monism. In the late 19th and early 20th century, the Church used St. Thomas’ thought, especially his theory of knowledge, to resist the temptations to Fundamentalism and Modernism when confronted with modern philosophy. And amid the revival of Thomism in the Neoscholastic movement, it was on the basis of St. Thomas’ anthropology and ethics that the Church codified Christian Social Teaching, with which she responded to secular humanism and totalitarian ideology in the 20th century.

St. Thomas also exerted a pervasive influence on the secular world. In the Second or Silver Age Scholasticism of the Renaissance and Baroque periods, Catholics and Protestants alike debated and speculated in theology, philosophy, and law using the thought of St. Thomas; and they laid upon his foundations the beginnings of international law, natural rights discourse, modern economic theory, and (through Suarez and Descartes) modern Western philosophy. In the past decades many non-Catholics rediscovered Thomism even as Catholics increasingly adopted non-Thomist modes of inquiry. Various schools now claim his authority for their competing theories on economics, sexual ethics, and social organization; and Aquinas’ epistemology and anthropology were recently cited as a superior basis to explain cognition and other neurological phenomena.

In sum, St. Thomas Aquinas may well be one of the greatest systematic philosophers in history, alongside Aristotle, Shankara, and Immanuel Kant; and he is certainly, with St. Augustine and St. John Damascene, one of the greatest theologians in the Catholic tradition. Therefore, while the Church has ever valued and learned from a plurality of intellectual schools, various Popes beginning with Leo XIII have specifically encouraged the study of St. Thomas’ mind and method, as did the Second Vatican Council; and St. Thomas is honoured in the Church as her “Angelic Doctor” and “Common Doctor”. At the Council of Trent, his Summa was placed upon the altar beside the Sacred Scriptures and the decrees of the Popes; and the Constitution Dei Filius of the First Vatican Council is to a great extent a restatement of St. Thomas’ teaching on faith and reason, itself founded on the doctrine of Scripture and the tradition of the Fathers.

All this attention would likely have nonplussed St. Thomas himself: a man of deep faith and humility who, after a great mystical vision, declared that all he had written was straw. In the university, his soft-spoken manner and (apparently) bovine appearance reportedly caused his fellow students to call him the “dumb ox”. It was left to his teacher Saint Albert the Great–himself a renowned theologian and pioneer of natural science–to correct them with the eventual judgment of posterity: “You call him a dumb ox, but I tell you… his bellowings shall fill the world.” Thus it is as much for his holiness and humility as for his brilliance that St. Thomas is held up as an example to Christian thinkers. Thus Pope Leo XIII declared:

“let us follow the example of the Angelic Doctor, who never gave himself to reading or writing without first begging the blessing of God, who modestly confessed that whatever he knew he had acquired not so much by his own study and labor as by the divine gift”. (Aeterni Patris, 33)

First posted on the Memorial of St. Thomas Aquinas in the Ordinary Form of the Roman Rite, 2013. Revised on the Feast of the Presentation of the Lord (Purification of the Blessed Virgin Mary) in the Roman Rite, 2013. Re-posted with minor modifications on the Memorial of St. Thomas Aquinas in the Ordinary Form of the Roman Rite, 2015.


*The Introduction is drawn in part from the article “St. Thomas Aquinas” of the Catholic Encyclopedia. It is also based on various works I’ve read in the past, including Joseph De Torre, Introduction to Christian Philosophy; Etienne Gilson, Elements of Christian Philosophy and The Spirit of Thomism; Frederick Copleston, Medieval Philosophy; Thomas Gilby, Poetic Experience: An Introduction to Thomist Aesthetic; and Joseph Pohle, Grace, Actual and Habitual: A Dogmatic Treatise.

[1] Summa Theologica, 1a 2ae, q.109, a.4, r.1.
[2] Summa Theologica, 1a, q.1, a.1, r.1.
[3] Summa Theologica, 1a, q.1, a.1, q.1, a.5, 1a 2ae, q.109, a.4, r.1.
[4] Summa Theologica, 1a, q.1, a.1, q.1, a.5; Summa Contra Gentiles, I, iv, 6.
[5] Summa Contra Gentiles, I, vii, 7.
[6] Summa Theologica, 1a, q.1, a.6, r.2.
[7] Summa Theologica, 1a 2ae, q.113, a.4.
[8] Summa Theologica, 1a 2ae, q.28, a.1-2; 2a 2ae, q.27, a.4.
[9] Summa Theologica, 1a 2ae, q.109, a.4c.
[10] Summa Contra Gentiles, V, liv, 9.
[11] Summa Theologica, 3a, q.49, a.1c.
[12] Summa Theologica, 3a, q.49, a.2.
[13] Summa Theologica, 3a, q.62, a.5.
[14] Summa Theologica, 1a 2ae, q.109, a9c, q.114, a.3c.
[15] Summa Theologica, 1a 2ae, q.3, a.8; q.5, a.5; q.114, a.4.

II. List of eBooks by St. Thomas Aquinas translated into English

(This a partial list of eBooks by St. Thomas Aquinas translated into English. There are more complete lists of the online works by St. Thomas Aquinas at the Aquinas Translation Project and Aquinas’ Works in English, and this list merely supplements them by indexing those works that are available in other websites.)

  1. Aquinas Ethicus: or, the Moral Teaching of St. Thomas. A Translation of the Principal Portions of the Second part of the Summa Theologica, with Notes by Joseph Rickaby, S.J. (London: Burns and Oates, 1892). Available in various formats at the Online Library of Liberty: Volume I and Volume II. [N.B. This text concisely presents the ethical ideas of St. Thomas by providing his Responsae and Replies to Objections.]
  2. Catena Aurea [Golden Chain of Commentaries on the Four Gospels], by St. Thomas Aquinas. May be read at Catechetics Online.
  3. Catena Aurea – 1 – The Gospel of Matthew – A Commentary on the Gospel by St. Thomas Aquinas. May be downloaded in PDF format through the Saints’ Books index,
  4. Catena Aurea – 2 – The Gospel of Mark – A Commentary on the Gospel by St. Thomas Aquinas. May be downloaded in PDF format through the Saints’ Books index,
  5. Catena Aurea – 3 – The Gospel of Luke – A Commentary on the Gospel by St. Thomas Aquinas.  May be downloaded in PDF format through the Saints’ Books index,
  6. Catena Aurea – 4 – The Gospel of John – A Commentary on the Gospel by St. Thomas Aquinas. May be downloaded in PDF format through the Saints’ Books index,
  7. Commentary on Boethius’ “On the Trinity” (Super Boethium De Trinitate), by St. Thomas Aquinas (c. 1250s). Questions 1-4, translated by Rose E. Brennan, S.H.N. (Herder, 1946). Questions 5-6, translated by Armand Mauer (Toronto, 1953). May be read online at the website of the Dominican House of Studies, Priory of the Immaculate Conception. Also available at the Logic Museum, which contains parallel Latin and English texts.
  8. Commentary on the Psalms, by St. Thomas Aquinas, translated by Stephen Loughlin, Hugh McDonald, Gregory Sadler, Steven DePangher, Ian Levy, Steve Perkins, James Miguez, Ed Redmond, Stephen P. Alcott, Peter Zerner, Alexander Hall, and Gregory Froelich. The commentaries on Psalms 1-54 are indexed at the Aquinas Translation Project, and (as corrected by Father Joseph Kenny, O.P.) on this page of his website. The Divine Lamp reproduces the commentaries on Psalm 3, Psalm 8, Psalm 10(9), Psalm 11(10), Psalm 15(14), Psalm 22(21), Psalm 23(22), Psalm 27(26), Psalm 30(29), Psalm 34(33), Psalm 36(35), Psalm 47(46), Psalm 51(50), and possibly others.
  9. Commentary on “The Sentences” of Peter Lombard, by St. Thomas Aquinas. Excerpt (Latin-English parallel texts) available on this page of the home page of Hugh McDonald. Various translated excerpts are indexed on the Aquinas Translation Project.
  10. Contra Errores Graecorum [Against the Errors of the Greeks], by St. Thomas Aquinas, O.P., translated by Peter Damian Fehlner, F.I., re-edited and missing chapters supplied by Joseph Kenny, O.P. May be read online at DHS Priory of the Immaculate Conception. [N.B., This work demonstrates that the Eastern Fathers affirm the teaching of the Catholic Church on points disputed by the schismatic Eastern churches.] [N.B.2, In his essay “St. Thomas Aquinas, Papal Supremacy, and the Witness of the Eastern Churches in the First Millennium”, online at Credo of Buffalo, James Likoudis refutes objections to St. Thomas’ citations of the Fathers.]
  11. [Explanation of the] Hail Mary, by St. Thomas Aquinas. Available on EWTN Library, as indexed on the St. Thomas Aquinas page of the Russian-language Medieval Philosophy Library.
  12. Explanation of the Lord’s Prayer, by St. Thomas Aquinas. Available on EWTN Library, as indexed on the St. Thomas Aquinas page of the Russian-language Medieval Philosophy Library.
  13. Explanation of the Sacraments, by St. Thomas Aquinas. Available on EWTN Library, as indexed on the St. Thomas Aquinas page of the Russian-language Medieval Philosophy Library.
  14. Explanation of the Ten Commandments, by St. Thomas Aquinas. Available on EWTN Library, as indexed on the St. Thomas Aquinas page of the Russian-language Medieval Philosophy Library.
  15. Meditations for Lent from St. Thomas Aquinas, by Saint Aquinas Thomas, 1225?-1274, translated by Philip Hughes (London: Sheed & Ward, 1917). With Imprimatur. Available on Internet Archive and Open Library (Digitizing sponsor: MSN; Book contributor: Regis College Library, University of Toronto).
  16. Metaphysics: Let Thomas Aquinas Teach It, edited by Joseph Kenny, O.P., St. Thomas Aquinas Priory (Ibadan, Nigeria, 2012). Available in PDF format at the website of Joseph Kenny. [N.B., This is a collection of texts by St. Thomas Aquinas, arranged thematically.]
  17. Philosophy of Nature: Let Thomas Aquinas Teach It, edited by Joseph Kenny, O.P., St. Thomas Aquinas Priory (Ibadan, Nigeria, 2012). Available in PDF format at the website of Joseph Kenny. [N.B., This is a collection of texts by St. Thomas Aquinas, arranged thematically.]
  18. The Political Ideas of St. Thomas Aquinas, edited with an introduction by Dino Bigongiari (New York: Hafner Publishing Co., 1953, repr. 1957). [Link deleted due to copyright concerns.]
  19. The Summa Contra Gentiles, by Saint Thomas Aquinas, translated by the English Dominican Fathers (London: Burns Oates & Washbourne, [NB, The source information states: New York: Benzinger Brothers], 1924). With Imprimatur. Available online at Saint Wiki.
  20. The Summa Contra Gentiles, or On the Truth of the Catholic Faith, by St. Thomas Aquinas, translated by Anton C. Pegis,  James F. Anderson, Vernon J. Bourke, and Charles J. O’Neil (New York: Hanover House, 1955-57). Edited, with English, especially Scriptural references, updated by Joseph Kenny, O.P.  Available at the Dominican House of Studies, Priory of the Immaculate Conception. Parallel texts in Latin and English available at the website of Joseph Kenny.
  21. The Summa Theologica [or Summa Theologiae, or Summation of Theology], by St. Thomas Aquinas, translated by the Fathers of the English Dominican Province (Second and Revised Edition, 1920). With Imprimatur. May be read on New Advent, with active links to relevant Scriptural passages and Catholic Encyclopedia articles. Another edition (Benziger Bros., 1947) is available on Catholic Primer and at the website of the Dominican House of Studies, Priory of the Immaculate Conception. The Logic Museum contains parallel Latin and English texts, the latter from the Dominican translation.
  22. The “Summa Theologica” of St. Thomas Aquinas. Part I. Literally translated by Fathers of the English Dominican Province. Second and revised edition (London: Burns Oates and Washbourne, 1920-1922). Available in various formats at the Online Library of Liberty: Volume I (Part I QQ I.-XXVI); Volume II (Part I, QQ XXVII-XLIX: Treatise on the Trinity, Treatise on the Creation); Volume III (Part I, QQ L.-LXXIV: Treatise on the Angels, Treatise on the Work of the Six Days);  and Volume IV (Part I QQ LXXV-CII: Treatise on Man).

III. Papal and Curial Statements on St. Thomas Aquinas

  1. Address to the Eighth International Thomistic Congress, by Pope John Paul II (13 September 1980). Available at Super Flumina.
  2. Aeterni Patris, Encyclical, On the Restoration of Christian Philosophy, by Pope Leo XIII (promulgated on 4 August 1879). Available at EWTN Library and at the Online Library of Liberty.
  3. Decree of Approval of Some Theses Contained in the Doctrine of St. Thomas Aquinas and Proposed to the Teachers of Philosophy, by the Sacred Congregation of Studies, translated from Latin by Hugh McDonald. Latin-English text available on this page of the home page of Hugh McDonald.
  4. Doctoris Angelici: Motu Proprio for Italy and the adjacent islands, to encourage the study of the philosophy of St. Thomas Aquinas in Catholic Schools, by Pope St. Pius X (1914). Available at The Summa.info.
  5. The Lives of the Saints: Catechesis on the Great Christian Writers of Both East and West, by Pope Benedict XVI (General Audiences 2007-2011). May be read online through Catechesis of the Popes. Includes: “St. Thomas Aquinas”  (June 2, 2010); “St. Thomas Aquinas: The Inter-Relation of Philosophy and Theology” (June 16, 2010); “St. Thomas Aquinas: The ‘Summa Theologica'” (June 23, 2010).
  6. Studiorem Ducem: Encyclical on St Thomas Aquinas, by Pope Pius XI, June 29, 1923. Available at The Summa.info.

IV. Some eBooks about St. Thomas Aquinas and His Works

This is a VERY small selection of the multitude of ebooks about St. Thomas Aquinas and his works that are legally available online. (Note that it excludes those texts that, while based on St. Thomas’ thought, does not have him or his work as its subject. I will post a separate list of such texts when I can, hopefully on the Feast of St. Thomas Aquinas in the Extraordinary Form of the Roman Rite.)

  1. Christ the Savior: A Commentary on the Third Part of St. Thomas‘ Theological Summa, by Reginald Garrigou-Lagrange, O.P. May be read online on EWTN Library and TheSumma.info.
  2. An Essay on Mediaeval Economic Teaching, by George Augustine Thomas O’Brien (London, New York [etc.] Longmans, Green, and co., 1920). Available in various formats at Internet Archive, Open Library, and Project Gutenberg. Another edition (Kitchener, Ontario: Batoche Books, 2001) is available in PDF format at the University of Manitoba Undergraduate Economics Society.
  3. Grace: Commentary on the Summa Theologica of St. Thomas, Reginald Garrigou-Lagrange, O.P. Dogmatic theology, Soteriology. May be read online on EWTN Library.
  4. Life Everlasting, by Reginald Garrigou-Lagrange, O.P. May be read online at Catholic Treasury.
  5. “The Moral Philosophy of St. Thomas Aquinas”, by Kenneth W. Kemp. Delivered at the Thomistic Conference, Vilnius, Lithuania, July 2000). 14 pages. Available in PDF format on this page of the University of St. Thomas.
  6. Moral Theology: A Complete Course Based on St. Thomas Aquinas and the Best Modern Authorities, by John A. McHugh, O.P. and Charles J. Callan, O.P., revised and enlarged by Edward P. Farrell, O.P. (New York City: Joseph F. Wagner, Inc.; London: B. Herder). With 1958 Imprimatur. Available in multiple formats at Many Books.net.
  7. “Nonlinear Brain Dynamics and Intention According to Aquinas”, by Walter J. Freeman, Mind and Matter: An International Interdisciplinary Journal of Mind-Matter Research, Vol. 6(2), pp. 207-234. Available in PDF format at Mind and Matter, with an abstract on this page. Also available in PDF format through Cite Seer X.
  8. The Physical System of St. Thomas, by Giovanni Maria Cornoldi, Edward Heneage Dering (London: Art and Book Co., 1893). Available at Internet Archive.
  9. Predestination, by Reginald Garrigou-Lagrange. The text, while not yet completely digitized, is available at The Summa.info.
  10. Providence, by Reginald Garrigou-Lagrange, O.P. Available at EWTN Library.
  11. Reality: A Synthesis of Thomistic Thought, by Reginald Garrigou-Lagrange, O.P. Available at EWTN Library.
  12. St. Thomas Aquinas, by G.K. Chesterton. Available at Chesterton’s Works on the Web. [N.B., This was pronounced by Etienne Gilson to be the best introduction to St. Thomas he had yet read.]
  13. St. Thomas Aquinas, by Jacques Maritain. May be read online at the online on this page of the Jacques Maritain Center (“Copyright by the Jacques Maritain Center, University of Notre Dame. All rights reserved”).
  14. St. Thomas Aquinas and Medieval Philosophy, by D.J. Kennedy, O.P. (New York: The Encyclopedia Press, Inc., 1919). Available at the Jacques Maritain Center.
  15. St. Thomas‘ Political Doctrine and Democracy, by Edward F. Murphy (Washington, D.C., Catholic University of America, 1921). Dissertation, 326 pages. Available in multiple formats at Internet Archive and Open Library, with a second copy at Internet Archive and Open Library. May also be read online at the Hathi Trust Digital Library.
  16. “Subsidiarity, Federalism and the Best Constitution: Thomas Aquinas on City, Province and Empire”, by Nicholas Aroney, Law and Philosophy, Vol. 26 (2007): pp. 161-228. University of Queensland TC Beirne School of Law Research Paper No. 07-06. Available in PDF format (70 pages) on the Social Science Research Network.
  17. A Tale of Two Wonderworkers: St. Nicholas of Myra in the Writings and Life of St. Thomas Aquinas, by Peter A. Kwasniewski, International Theological Institute for Studies on Marriage and the Family, Gaming, Austria [Footnote 1 states: “This article was developed from a lecture given at the International Theological Institute on December 6, 2002.”]. Available in PDF format at DeSales University.
  18. “Thomas Aquinas on Justice as a Global Virtue”, by Claus Dierksmeier. Available in PDF format through the Social Science Research Network [N.B. The text may be of interest in the application of Catholic Christian ethics in the Thomist tradition.]
  19. A Tour of the Summa, by Monsignor Paul J. Glenn. May be read online at CatholicTheology.info. Described thus at Marian Land: “This unique synopsis of the Summa Theologica is a complete, chapter-by-chapter restatement of St. Thomas’ work, intended to expose readers to the totality of St. Thomas’ thought and yet be brief enough to fit into one volume.”
  20. The Trinity and God the Creator, Reginald Garrigou-Lagrange, O.P. Dogma. May be read online on EWTN Library.
  21. Thomism and Mathematical Physics, Dissertation by Bernard I. Mullahy (July 1946). Available on Internet Archive. (Creative Commons license: Attribution-Share Alike 3.0)
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