LECTURE 20 (221 a 1-222 a 9)

HOW MOTION AND OTHER THINGS ARE IN TIME. WHAT THINGS ARE AND WHAT THINGS ARE NOT IN TIME

             600. After the Philosopher has treated time in itself, he here treats time in comparison with those things which are in time.

             Concerning this he makes two points. First he compares time to those things which are in time. Secondly, where he says, 'The "now" is the link . . .' (222 a 10), he compares time to those things which are in the 'now'.

             Concerning the first part he makes two points. First he compares time to motion. Secondly, where he says, 'Clearly then "to be in time" . . .' (221 a 8), he compares time to other things which are in time.

             601. Concerning the first part it must be realized that motion is compared to time differently than other things are. For motion is measured by time both in respect to what it is and in respect to its duration or its existence. Other things, like a man or a stone, are measured by time in respect to their existence or their duration, insofar as they have a changeable existence. But in respect to what they are, they are not measured by time but rather the 'now' of time corresponds to them, as was said above.

             Therefore, he says that time is the measure both of motion itself and of being moved, by which he means the duration of motion.

             Moreover, time measures motion in that it determines some part of the motion which measures the whole. And this is necessarily so, for everything is measured by something of the same genus, as is said in Metaphysics, X. This is clear in the measurement of magnitude. For a cubit measures the whole length of a road or a piece of cloth by determining some part of its length, which then measures the whole. Likewise time measures the whole of a motion by means of a part. For by the motion of one hour the motion of a whole day is measured, and by the daily motion the motion of a year is measured. Therefore, for motion to be measured by time is nothing else than for motion to be in a time which is measured by time, both in respect to what it is and in respect to its duration. For motion is measured by time in both respects, as was said.

             602. Next where he says, 'Clearly then "to be in time" . . .' (221 a 8), he explains how time is related to other things. First he explains how other things are in time. Secondly, where he says, 'Since what is "in time" . . .' (221 a 26), he explains what things can be in time.

             He says, therefore, first that motion is in time when it and its existence are measured by time. Hence it is clear that other things are also in time and are measured by time. But only their existence is measured by time, not they themselves. For motion is per se measured by time, but other things are measured by time only insofar as they have motion.

             He shows as follows that for a thing to be in time means that its existence is measured by time. To be in time can be understood in two ways. First, a thing is said to be in time when it is together with time. Secondly, things are said to be in time just as things are said to be in number. This latter has two meanings. First, a thing is said to be in number as a part, as two is in four, or as its proper passion, like even and odd, or whatever else belongs to number. Secondly, a thing is said to be in number, not because it itself is a number, but because number belongs to it as a numbered thing, as men are said to be such and such in number.

             Now since time is a number, things exist in time in both ways. For the 'now', and the before and after, and other such things are in time in the same way that unity, which is a part, and even and odd, which are passions of number, and the perfect and the superfluous, are in number. (A number is perfect when it consists of parts which measure it. For example, the number six, which is measured by one, two, and three, is constituted by these numbers taken together. A number is superfluous when the parts which measure it exceed the whole. For example, the number twelve is measured by one, two, three, four and six, but these numbers taken together total sixteen.) In this way some things are in time because they pertain to time. But things which do not pertain to time are said to be in time as things which are numbered are in number. Hence it is necessary that things which are in time are contained under time as under a number, just as things which are in place are contained under place as under a measure.

             Next he examines the first way of existing in time. He says that it is clear that to be in time, and to be when time is, are not the same thing. In the same way to be in motion and in place is not the same as to be when place and motion exist. Otherwise it would follow that all things are in each thing; for example, the heavens would be in a grain of wheat. For when the wheat exists, the heavens also exist.

             Moreover, there is the following difference between these two things. When a thing is said to exist when something else exists, it is accidental to the one that it exists simultaneously with the other. But that in which a thing is as in a measure follows with necessity. Thus time necessarily is consequent upon that which exists in time. And motion necessarily is consequent upon that which is in motion, since they exist together.

             603. Next where he says, 'Since what is "in time" . . .' (221 a 26), he shows what things can be in time.

             First he shows that not every being is in time. Secondly, where he says, 'Plainly, then, neither . . .' (221 b 23), he shows that not all non-beings are in time.

             Concerning the first part he makes two points. First he shows that things which always exist are not in time. Secondly, where he says, 'Since time is the measure . . .' (221 b 7), he shows that even things which are at rest are, as such, in time.

             Concerning the first part he makes two points. First he sets forth certain things from which he establishes his position. Secondly, he comes to his conclusion, where he says, 'Hence, plainly, things . . .' (221 b 3).

             He sets forth two points. First, when a thing is in time as the numbered is in number, it is necessary that there can be a time which is greater than anything which is in time, just as there can be a number which is greater than anything which is numbered. And because of this it is necessary that all things which are in time are totally contained and included under time, just as things which are in place are included under place.

             604. He gives the second point where he says, 'A thing, then, will be . . .' (221 a 30). Everything which is in time suffers something under time, insofar as passion pertains to the imperfect. He proves this by means of our customary way of speaking. For we are accustomed to say that a long time weakens and corrupts, and that because of time all things in time grow old, and that because of time forgetfulness occurs. For things which we recently knew remain in the memory, but they slip away during the passage of time.

             And lest someone should say that perfections should also be attributed to time as are the passions, he next refutes this view. He gives three arguments against the above three points.

             Against his point that forgetfulness occurs because of time, he adds that one does not learn because of time. For if one lives for a long time undisturbed by the desire to learn, he does not thereby learn. And thus because of time he forgets.

             Against his point that all things grow old in time, he adds that nothing new is done because of time. For from the mere fact that a thing lasts a long time it does not become new, but rather becomes old.

             Against his point that time wastes things away, he adds that time does not make a thing good, that is, perfect and whole, but rather weakened and corrupted. The reason for this is that some things are corrupted by time, even if that which corrupts them is not clearly apparent. This is seen in the very nature [ratio] of time. For time is the number of motion. It is the nature [ratio] of motion to separate that which is from a disposition in which it formerly was. Hence, since time is the number of the first motion by which mutability is caused in all things, it follows that because of the passage of time all things in time are removed from their own dispositions.

             605. Next where he says, 'Hence, plainly, things . . .' (221 b 3), he draws his conclusion from the premises, and first from the first premise. It was shown that anything which is in time is contained under time. But things which always exist are not contained under time as something which exceeds. Nor is the duration of these things measured under time. For they endure to infinity, and the infinite cannot be measured. Therefore, things which always exist are not in time. This is true insofar as they exist always. For the celestial bodies always exist according to the existence of their substance, but not according to their place. Therefore, their duration is not measured by time, but their local motion is measured by time.

             Secondly, where he says, 'A proof of this . . .' (221 b 5), he proves the same thing from the second premise. He says that a sign of the fact that things which always exist are not in time is that they do not suffer from time, as though they were not existing in time. For they do not waste away or grow old, as was said of things which are in time.

             606. Next where he says, 'Since time is the measure . . .' (221 b 7), after he has shown that things which always exist are not in time, he examines in the same way things which are at rest. One might believe that things which are at rest, as such, are not measured by time. Hence, to refute this he shows that time is also the measure of rest.

             Concerning this he makes five points. First he states his intention. He says that, since time is the measure of motion per se, it will be the measure of rest per accidens. For all rest is in time, as is all motion.

             607. Secondly, where he says, 'For it does not follow . . .' (221 b 9), he denies a certain point from which it would seem that rest is not measured by time. Since time is the measure of motion, one might believe that rest is not in time since it is not in motion. Therefore, to refute this, he says that it is not necessary that everything which is in time be moved, as it is necessary that everything which is in motion be moved. For time is not motion, but the number of motion. Moreover, there happens to be in the number of motion not only that which is moved but also that which is at rest.

             608. Thirdly, where he says, 'Not everything that is . . .' (221 b 12), he proves the proposition that rest is in the number of motion, such that it is measured by time.

             To prove this he points out that not everything which is not moved is at rest. Rather rest is a privation of motion in that which can be moved. As was said above in Book III, that whose immobility is rest is moved, for rest is not the negation of motion, but its privation. Thus it is clear that the existence of a being at rest is the existence of a mobile thing. Hence, since the existence of a mobile thing is in time and is measured by time, the existence of a thing at rest is also measured by time. Moreover, we say that a thing is in time as in a number because there is some number of that thing and because its existence is measured by the number of time. Hence it is clear that rest is in time and is measured by time, not insofar as it is rest, but insofar as it is mobile. And because of this he stated above that time is the measure of motion per se and of rest per accidens.

             609. Fourthly, where he says, 'But time will measure . . .' (221 b 16), he shows how that which is mobile and that which is at rest are measured by time.

             He says that time measures that which is moved and is at rest, not insofar as it is a stone or a man, but insofar as it is moved and is at rest. For measurement properly belongs to quantity. Therefore, that is properly measured by time whose quantity is measured by time. From the measurement of time is known the quantity of motion and the quantity of rest, but not the quantity of that which is moved. Hence, that which is moved is not simply measured by time according to its proper quantity, but according to the quantity of its motion. From this it is clear that time is properly the measure of motion and rest; of motion per se, and of rest per accidens.

             610. Fifthly, where he says, 'Thus none of the things . . .' (221 b 21), he points out a corollary of the above. If a thing is measured by time only insofar as it is moved and is at rest, it follows that things which are neither moved nor at rest, as the separated substances, are not in time. For to be in time is to be measured by time. And time is the measure of motion and of rest, as is clear from what has been said.

             611. Next where he says, 'Plainly, then, neither . . .' (211 b 23), he shows that not all non-beings are in time.

             He says that it is clear from the above that not every non-being is in time, for example, those things which cannot be otherwise, as if the diameter were commensurable with the side of a square. This is impossible because it can never be true. Such things are not measured by time.

             He proves this as follows. Time primarily and per se is a measure of motion, and other things are measured by time only per accidens. Therefore, whatever is measured by time happens to be moved or to be at rest. Hence generable and corruptible things, and anything which at one time is and another time is not, are in time because they are moved and are at rest. For there is a certain time greater than they, which excels their duration, and because of this it measures their substances, not according to what they are, but according to their existence or duration.

             Among things which are not, but nevertheless are contained by time, certain ones at some time were, as Homer; certain ones at some time will be, as a future event; or if they are contained by past and future time, they were and will be. Those things which in no way are contained by time neither are nor were nor will be. Such things always are not, and their opposites always are. Thus the diameter is always incommensurable with the side. Hence this is not measured by time. And because of this its contrary, that the diameter is commensurable with the side, is not measured by time. Therefore, it always is not because it is contrary to that which always is.

             That whose contrary is not always can be and not be, and is generated and corrupted. Such things are measured by time.