is demonstrations says, "Let this line be infinite." Therefore it is
not impossible for a thing to be infinite in magnitude.

Obj. 2: Further, what is not against the nature of anything, can
agree with it. Now to be infinite is not against the nature of
magnitude; but rather both the finite and the infinite seem to be
properties of quantity. Therefore it is not impossible for some
magnitude to be infinite.

Obj. 3: Further, magnitude is infinitely divisible, for the
continuous is defined that which is infinitely divisible, as is clear
from Phys. iii. But contraries are concerned about one and the same
thing. Since therefore addition is opposed to division, and increase
opposed to diminution, it appears that magnitude can be increased to
infinity. Therefore it is possible for magnitude to be infinite.

Obj. 4: Further, movement and time have quantity and continuity
derived from the magnitude over which movement passes, as is said in
Phys. iv. But it is not against the nature of time and movement to be
infinite, since every determinate indivisible in time and circular
movement is both a beginning and an end. Therefore neither is it
against the nature of magnitude to be infinite.

_On the contrary,_ Every body has a surface. But every body which has a
surface is finite; because surface is the term of a finite body.
Therefore all bodies are finite. The same applies both to surface and
to a line. Therefore nothing is infinite in magnitude.

_I answer that,_ It is one thing to be infinite in essence, and another
to be infinite in magnitude. For granted that a body exists infinite
in magnitude, as fire or air, yet this could not be infinite in
essence, because its essence would be terminated in a species by its
form, and confined to individuality by matter. And so assuming from
these premises that no creature is infinite in essence, it still
remains to inquire whether any creature can be infinite in magnitude.

We must therefore observe that a body, which is a complete magnitude,
can be considered in two ways; mathematically, in respect to its
quantity only; and naturally, as regards its matter and form.

Now it is manifest that a natural body cannot be actually infinite.
For every natural body has some determined substantial form. Since
therefore the accidents follow upon the substantial form, it is
necessary that determinate accidents should follow upon a determinate
form; and among these accidents is quantity. So eve