An Introduction to PhilosophyFullerton, George Stuart
Philosophy
An Introduction to Philosophy
Fullerton, George Stuart
Philosophy
It was pointed out many centuries ago that it is equally inconceivable
that there should be a _very first_. How can a point even begin to
move along an infinitely divisible line? Must it not before it can
move over any distance, however short, first move over half that
distance? And before it can move over that half, must it not move over
the half of that? Can it find something to move over that has no
halves? And if not, how shall it even start to move? To move at all,
it must begin somewhere; it cannot begin with what has no halves, for
then it is not moving over any part of the line, as all parts have
halves; and it cannot begin with what has halves, for that is not the
beginning. _What does the point do first?_ that is the question.
Those who tell us about points and lines usually leave us to call upon
gentle echo for an answer.
The perplexities of this moving point seem to grow worse and worse the
longer one reflects upon them. They do not harass it merely at the
beginning and at the end of its journey. This is admirably brought out
by Professor W. K. Clifford (1845-1879), an excellent mathematician,
who never had the faintest intention of denying the possibility of
motion, and who did not desire to magnify the perplexities in the path
of a moving point. He writes:--
"When a point moves along a line, we know that between any two
positions of it there is an infinite number . . . of intermediate
positions. That is because the motion is continuous. Each of those
positions is where the point was at some instant or other. Between the
two end positions on the line, the point where the motion began and the
point where it stopped, there is no point of the line which does not
belong to that series. We have thus an infinite series of successive
positions of a continuously moving point, and in that series are
included all the points of a certain piece of line-room." [1]
Thus, we are told that, when a point moves along a line, between any
two positions of it there is an infinite number of intermediate
positions. Clifford does not play with the word "infinite"; he takes
it seriously and tells us that it means without any end: "_Infinite_;
it is a dreadful word, I know, until you find out that you are familiar
with the thing which it expresses. In this place it means that between
any two positions there is some intermediate position; between that and
either of the others, again, there is some other intermediate; and so
on _without any end_. Infinite means without any end."
But really, if the case is as stated, the point in question must be at
a desperate pass. I beg the reader to consider the following, and ask
himself whether he would like to change places with it:--
(1) If the series of positions is really endless, the point must
complete one by one the members of an endless series, and reach a
nonexistent final term, for a really endless series cannot have a final
term.
Public-domain text, read in full here on John Shaqi.
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