@hatsoff: I think you might be misunderstanding the argument, since Aquinas DID in fact believe it possible for time to extend back into infinity, and impossible to rationally prove otherwise - in other words, in his view the creation of the universe at a point in time is a matter of faith alone. (You should know that he was wrong, however - we know from science that it did begin in a point of time 13.7 billion years ago.)
Cecilianus:
Aquinas was never absolutely sure that the universe was infinite. That being said, he did believe that in a series of movers that are only accidentally subordinated to one another, an actual infinity is possible. (
Summa Theologica, I, q. 46, a. 2, reply 7.) However, he did not believe that a series of essentially subordinated movers could regress infinitely. However, now that we’re at least pretty sure that the universe is only about 10 - 20 billion years old, which St. Thomas could not have known, we can surmise that even an accidentally subordinated series cannot be infinite.
My understanding of motion, which I got from a college natural theology class, was that for Aquinas it was a change which was caused simultaneous with its cause (e.g., when I lift a heavy object, my act of lifting is simultaneous with the being-liftedness of the object) -
Close, but not quite. Think about it this way. If my arm moves a stick that, in turn, moves a ball along the ground, I have a simple example of a series of movers. As you can no doubt see, there are (at least) three exigencies of this motion: the arm (or first mover - in this example), the stick (or second mover), and finally, the ball, which is moved. The stick is being moved by the arm - and it is moved simultaneously. The arm is moving with the stick and the ball, simultaneously. The ball is being moved, simultaneously by the stick and the arm.
this is what distinguishes the First Way from the Second Way.
Not so. They are essentially two ways of explaining the same phenomenon. Aquinas explains “motion” first in order to more adequately explain causing, which then makes it easier to understand God as the Cause of causes.
(That is, we wouldn’t describe an event today as being “moved” by the Big Bang, even though that was how it came into existence 13.7 billion years ago.)
Although there are things that are moving today that were set in motion by the Big Bang. How inertia works may not be as well understood from Newton’s Axioms, as they seem to describe only that outside forces can modify forward motion. There are theories that describe what keeps a particular mass in motion, in the absence of external impediments. So, in that sense you are correct.
However, I believe that hatsoff’s remark about the only change he knows of being physical change extended over time is true in our modern, physical understanding of the world, since atoms and energy can only move at a finite speed.
All change is involved in time, in some way. That being said, change caused by an essentially subordinated series of movers is simultaneous change. But, in time, there is the exigency known as the
Now. The
Now is something very distinct from anything that is part of the continuum of time. Simply, it is the last exterior
surface of the terminus of a time slice and the first exterior
surface of the beginning of the ensuing, new time slice. We know that it exists, but, we cannot describe in any but those terms. We cannot even recall that nano-instant (for lack of a better word), yet we know that it just passed us by.
Second point I wanted to make to you: Logic and mathematical realities are universally true and exist outside of our mind. I say this because you can’t do science without them. As a student of physics I cannot make sense of what I do without assuming the truth of mathematics. Even if there were nobody around to think about it, 2 + 2 would still equal 4.
However, do not forget that as the human mind abstracts from physical reality, it must perform an additional abstraction in order to grasp the “matter” of mathematics. The first abstraction takes the mind from the sensible world to the order of individual intelligible matter. The second abstraction, takes us to the universal or common consideration of intelligible matter. In this sense, it is not physically real. Number does not burn; nor does it have any kind of texture, nor does it have mass. One cannot throw a circle and sever a head. Mathematics is the consideration of
quantified substance, and though it may exist in the absence of man or, any other living creature that can count, it is utterly meaningless - except perhaps to God.
@Detales: Metaphysics is the study of being, and as such there is an ambiguity: By Being do we mean God, or do we mean the world of beings around us maya? In scholastic philosophy the words Being and Metaphysics are used to describe both, with God being the summit of the science of Metaphysics (in the order in which we study them) and the Principle of the subject of Metaphysics (in the order of reality). Since God is eternal and unchanging, motion (change, in the medieval [modern, too] use of the word) occurs only in the world, not in God; but God is viewed as the origin of motion while Himself being unmoved (the “Unmoved Mover”), hence we call it “metaphysical motion”. I would agree with your statement that the term “metaphysical” is technically less than perfectly correct, however.
This does not seem quite correct, but, I’m not sure why at this moment.
continued . . .