Kreeft Enlightens Aquinas’ Summa

Peter Kreeft A Shorter SummaPeter Kreeft.[1]1993. A Shorter Summa: The Essential Philosophical Passages of St. Thomas Aquinas’ Summa Theologia Edited and Explained. San Francisco: Ignatius Press.

Review by Stephen W. Hiemstra

In college back in the 1970s, I felt compelled to read the classics of the Christian faith. That effort led me to explore authors such as Augustine, Edwards, Lewis, Little, and so on. Aquinas capped my quest and brought it to an end: where do you start and how do you get past the first page? Aquinas proved incomprehensible and I soon abandoned my effort.

Peter Kreeft’s A Shorter Summa begins:

“This is a shortened version of Summa of the Summa, which in turn was a shortened version of the Summa Theologiae (Summa Theologica). The reason for the double shortening is pretty obvious: the original runs some 3,000 pages…The Summa is certainly the greatest, most ambitious, most rational book of theology ever written.” (ii)

Perhaps, I was not the first student intimidated by Thomas Aquinas’ Summa Theologica!

Who is Peter Kreeft?

Peter Kreeft is a professor of philosophy at Boston College, a Jesuit (Catholic) university, and author of over seventy-five books. He is a graduate of Calvin College (1959). His masters and doctorates are from Fordham University (1961, 1965). He also did post-graduate studies at Yale University. He was raised in the Reformed Church in America, but later became a Roman Catholic.[2]

Why Read Thomas Aquinas?

Kreeft believes that Aquinas is the greatest philosopher (Italian, 1225-1274) who ever lived and offers eight reasons:

  1. Aquinas told the truth, which is the mark of a philosopher—one who loves knowledge.
  2. Common sense. Aquinas’ ethics are in Kreeft’s view: “practical and plain and reasonable”
  3. Aquinas was someone that popes and kings wrote to for advice.
  4. Aquinas was someone who seems obscure at first but clearer with each reading.
  5. Aquinas strived for clarity and focused on things that the average person wonders about—God, man, life, death, good and evil.
  6. Kreeft writes: “Even non-Catholics must go to St. Thomas to understand Catholic theology and philosophy. You never understand a philosophy from its critics or dissenters.”
  7. Aquinas epitomized the medieval mind.
  8. Aquinas is a standard by which to highlight the modern era for all of its differences and weaknesses. (13-16)

At some point, I remember reading that while Augustine introduced the Christian world to Plato, in like manner Aquinas introduced Aristotle. While Plato focused on theoretical knowledge (transcendent), Aristotle focused on empirical knowledge revealed by the senses (immanent). Inasmuch as postmodern people have trouble with transcendence, the current focus on the immanent suggests that returning to Aquinas is especially important for postmoderns.

Postmoderns also seem to have trouble hearing each other’s perspectives, Aquinas respected his critiques and painstakingly argued both sides of a controversy in the Summa Theologicabefore offering his own conclusion.

More generally, Kreeft sees Aquinas as more of an encyclopedia than a textbook. (17) For those born after Wikipedia, an encyclopedia once provided an important resource that students would consult before striving to understand other resources.

Organization of the Summa

Kreeft outlines the Summa as a circle that begins and ends with God. The movements around the circle include:

God (at top)

  • His essence in terms of whether and how he exists and how he operates,
  • His three persons

Creation (left side)

Man (bottom)

Man’s return to God (Right side at bottom)

Christ—man’s way to return to God (right side further up)

Kreeft describes the Summa “not like information in a library, but like blood in a body.” He describes the Summa as written in a choppy style because arguments are divided up into bite-sized pieces. (18)

Organization of the Book

Kreeft sees his book as distinctive from other summaries of the Summa in four ways:

  1. He focuses on Aquinas’ own words.
  2. He relies on an older, literal Dominican translation.
  3. He focuses only on the Summa. and
  4. He includes numerous explanatory footnotes. (22)

He also writes for beginners in philosophy; leaves out arguments not interesting to modern discussion, and focuses on Aquinas’ chief arguments relevant to philosophy, not theology per se (ii).

Kreeft begins his book with a preface, introduction, and glossary, then writes his text in seven chapters:

  1. Methodology: Theology as a Science
  2. Proofs for the Existence of God
  3. The Nature of God
  4. Cosmology: Creation and Providence
  5. Anthropology: Body and Soul
  6. Epistemology and Psychology
  7. Ethics(contents)

Not trained in philosophy, I found the glossary most helpful.

For example, I particularly enjoyed his definitions of a:

“syllogism: (1) logical argument; (2) especially a deductive argument; (3) especially a certain deductive argument with three terms, two premises, and one conclusion.” (35)

Uncertain over the years about the third definition, I felt badly about using the first one!


Kreeft warns students to review their understanding of “basic, common sense logic”(19) and explains that Aquinas normally states his premises in a form capable of a yes-no answer. For example, in the first chapter on the Nature and Extent of Sacred Doctrine, he asks: “Whether, besides Philosophy, Any Further Doctrine is Required?”(39) He observes that the Summa is not so much a systematic theology, but a “summarized debate”(17).

Kreeft’s footnotes are worth their weight in gold. One footnote, for example, offers twenty-four arguments for God’s, starting with the ontological argument put forward by Anselm (56-58). Another gem highlights the three meanings of logos in Greek—intelligent being, intelligence, and communication—and how these three meanings inform the philosophical eras—metaphysics (ancient and medieval periods), epistemology (classical modern period), and language (contemporary period) (65-66).

Aquinas’ own arguments are priceless. For example, he argues that our happiness cannot be attributed to fame or glory because “for human knowledge is caused by the things known, whereas God’s knowledge is the cause of the things known.”(138)

Aquinas is also the source of a lot of wisdom that seems to float around today without an obvious source. For example, Aquinas argues that the four cardinal virtues are prudence, justice, temperance, and fortitude, while the three theological virtues are faith, hope, and love, as taken from1 Corinthians 13:13 (153-155).


Peter Kreeft’s A Shorter Summa is a most helpful introduction to St. Thomas Aquinas’ Summa Theologica. For those of us exposed to Aquinas who never quite understood him, this is a wonderful little book. Philosophy and seminary students and working pastors will find this book interesting and useful. I wish that I had had this book back when I was in college.


 Kreeft, Peter (Editor). 1990. A Summa of the Summaby Thomas Aquinas. San Francisco: Ignatius Press.



Kreeft Enlightens Aquinas’ Summa

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