Born in Aquino, Italy, Saint Thomas Aquinas (1225-1274) was noted for his scholastic synthesis of the philosopher Aristotle and Christian theology. This Dominican monk taught at the University of Paris and was best known for his two “summations” of medieval thought, Summa Theologica and Summa Contra Gentiles, but wrote in many other genres including Bible commentaries, all of which exerted a lasting influence on Christian thought.
Beginning with Boethius, medieval Catholic theologians had disagreed about the concept of time; among Aquinas’s important achievements was his sorting out of these arguments. Aquinas’s best discussion of time is in the first book of the Summa Theologica, Question 10, which discusses the eternality of God and compares eternity to time. Aquinas brings out six points of inquiry.
First, what is a good definition of eternity? Aquinas bases his definition on one given by Boethius in his De Consol: “Eternity is the simulta- neously-whole and perfect possession of interminable life.” Some scholars have stated that the use of the word interminable connotes a negative assessment of eternity. Also, the word life does not match with the ontological definition of eternity. The whole is improper when compared to the simplicity of eternity. Eternity is not instantaneous. The whole and the perfect are redundant. Also, eternity is not a possession. In response, Aquinas appeals to simplicity; for that, human beings must understand eternity by means of time. Time is both being and living. Time is the apprehension of the measuring of movement by the causality of time in the past and the future. Later in the first book, Aquinas saw the existence of time as a measure of duration. Therefore, eternity is the holistic and perfect apprehension of what is outside of movement. We can measure time, because it has a beginning and an end. Eternity is immeasurable. So what is eternal is interminable and has no succession and cannot be possessed.
Second, is God eternal? Some scholars object that because God is the creator of eternity, so he cannot be eternal. God is before and after eternity. One can measure eternity but not God. Time (as past, present, and future) is applied to God in the Bible, although the creeds apply eternality to God. In reply, Aquinas connects time to change, and eternity to immutability. Yet, God is not eternal only; but God is “His own eternity.” For Aquinas, this is a “participated eternity” utilized from scripture through royal metaphors and images of time so that we may understand that eternity is nothing else but God himself.
Third, does eternality belong to God alone? While some see eternality in righteousness, judgment, and necessity, Aquinas said that because God alone is eternal, only God’s sharing that eter- nality with his creation would allow someone or something other than God to be eternal.
Fourth, how does eternity differ from time? Some object to the difference between eternity and time because time is a part of eternity, their natures differ, and eternity swallows up time. Yet, a disagreement may arise because time has a “before” and an “after.” For Aquinas, they are two different things, for eternity has a permanence and time is “a measure of movement: . . . that eternity is simultaneously whole, but that time is not so.”
Fifth, how does aeviternity differ from time? Aeviternity (sometimes translated “everlasting” or “endless”) is the eternity shared by God on the creation. For some thinkers, there is no difference between aeviternity and time because both measure duration and neither is eternal. Aquinas answers that they do differ and that aeviternity stands between time and eternity. While some differentiate among the three concepts in that “eternity has neither beginning nor end, aeviternity, a beginning but no end, and time both beginning and end” Aquinas sees this as an “accidental” case. Other thinkers then see a distinction based on “something old and something new”: these three to consist in the fact that eternity has no “before” and “after” but that time has both, together with innovation and veteration, and that aeviternity has “before” and “after” without innovation and veteration.
Aquinas disagreed with this contradiction in terms: “The being that is measured by eternity is not changeable, nor is it annexed to change. In this way time has ‘before’ and ‘after’; aeviternity in itself has no ‘before’ and ‘after,’ which can, however, be annexed to it; while eternity has neither ‘before’ nor ‘after,’ nor is it compatible with such at all.”
And the sixth and final study is whether there is only one aeviternity. Some thinkers argued that there are multiple aeviternities based on all the spiritual entities in heaven. For others, aeviternity “is [a] more simple thing than time, and is nearer to eternity.” Aquinas answers with a discussion that ties the oneness of time to aevi- ternity: “Therefore time is referred to that movement, not only as a measure is to the thing measured, but also as accident is to subject; and thus receives unity from it” For Aquinas, it would be necessary to say that there is one aevi- ternity only.
Saint Thomas Aquinas showed a difference between eternity, aeviternity, and time. Eternity has neither a beginning nor an end. Only God is eternal. Aeviternity has a beginning but has no end. Only the part of creation that accepts God’s gift of eternity takes part in it. Then, time is the measured duration of movement that has a beginning and an end.
See also Aquinas and Aristotle; Aquinas and Augustine; Aristotle; Augustine of Hippo, Saint; Avicenna; Bible and Time; Boethius, Anicius; Christianity; Eternity;
God and Time; God as Creator; Teleology; Time, End of; Time, Sacred
Davies, B. (1993). The thought of St. Thomas Aquinas. Oxford, UK: Oxford University Press.
Leftow, B. (1990). Aquinas on time and eternity.
American Catholic Philosophical Quarterly, 64, 387-399.
Torrell, J.-P. (2005). Saint Thomas Aquinas.
Washington, DC: Catholic University of America.