CHAPTER ONE:
ST. THOMAS AQUINAS
ject and aspect; and hence eternity is not the same as the now of time.
Reply Obj. 3. As eternity is the proper measure of permanent being, so time is the proper measure of movement; and hence, according as any being recedes from permanence of being, and is subject to change, it recedes from eternity, and is subject to time. Therefore the being of things corruptible, because it is changeable, is not measured by eternity, but by time; for time measures not things only.* }
ST. THOMAS WROTE A LITTLE TREATISE ON THE PROBLEM
of essence and existence. Concerning Being and Essence is one of the most astonishingly lucid of all St. Thomas's works and is today still one of the most apposite; it is given here** in part.
{ INTRODUCTION:
Because a small error in the beginning is a great one in the end, according to the Philosopher in the first book of the De Caelo et Mundo, and since being and essence are what are first conceived by the intellect, as Avicenna says in the first book of his Metaphysics, therefore, lest error befall from ignorance of them (being and essence), in order to reveal their difficulty it should be said what is signified by the names being and essence, and how they are found in diverse things and how they are disposed with respect to logical intentions, namely, genus, species, and difference.
CHAPTER ONE:
Because indeed we must receive knowledge of the simple from the composite and arrive at what is prior from what is posterior, in order that beginning with the less difficult
* Reprinted from the Summa Theologica with the permission of Benziger Brothers, Inc., publisher and copyright owners.
**From:
St. Thomas Aquinas' Concerning Being and Essence trans. George C. Leckie (Copyright 1937, D. Appleton-Century
Co., Inc. Reprinted by permission of the publishers, AppletonCentury Crofts, Inc.).
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THE AGE OF BELIEF
_ instruction may be made more suitably, we should proceed _ from the meaning of being to the meaning of essence.
Therefore one should know, as the Philosopher says in the fifth of the Metaphysics, that being by itself is said to be taken in two modes: in the one mode, that it is divided into - ten genera; in the other, that it signifies the truth of propositions. Moreover the difference between these is that in the second mode everything can be called being concerning which an affirmative proposition can be formed, even if it posits nothing in the thing, by virtue of this mode privations
_ and negations are likewise called beings, for we say that affirmation is the opposite of negation, and that blindness is in the eye. But in the first mode only what posits something in the thing can be called being; consequently, according to the first mode blindness and such are not beings. The name essence, therefore, is not taken from being in the second mode, for in this mode some things are said to have essence which have not being, as is evident in privations. But essence is taken from being only in the first mode; whence the Commentator says in the same place that "being in the first mode is said to be what signifies the essence of the thing." And because, as has been said, being in this mode is divided into ten genera, it follows that essence signifies something common to all natures by which diverse beings are disposed in different genera and species, as for instance humanity is the essence of man and so for others. And because that by means of which the thing is constituted in its proper genus or species is that which is signified by the definition indicating what the thing is, hence it is that the name essence has been changed by philosophers into the name quiddity. And this is what the Philosopher frequently calls "quod quid erat esse," that is, that by virtue of which a thing (anything) has to be what it is (something).
And indeed it is called form according as by means of form the certitude of any single thing is signified, as Avicenna remarks in the second part of his Metaphysics. This is called by another name, nature, accepting nature according to the first of the four modes assigned by Boethius in his book De Duabus Naturis, namely, according as nature is said to be all that which can be comprehended by the