You can have an infinite number of intervals in an interval of finite length:. [0,1/2), [1/2, 3/4), [3/4, 7/8), [7/8, 15/16),… will be an infinite number of intervals in [0,1].
In any case, there are an infinite number of split seconds in a one hour interval follows from what you have shown. There are 3600 seconds in one hour.
There are 2x3600 split seconds of length 1/2
There are 4x 3600 split seconds of length 1/4
There are 8x 3600 split seconds of length 1/8
There are 16x 3600 split seconds of length 1/16
There are 32x 3600 split seconds of length 1/32
Etc. There is no limit to the number of split seconds in a one hour interval.
Everyone knows that. But that’s not an actual infinite, that’s a potential infinite. The difference between 2 and 1 is 1. The fact that you “can” divide the intervals indefinitely shows that there is a potentially infinite number of intervals, but they’re not actual.
For any natural number n, n+1, or n/2 is always a finite number, therefore not an actual infinite – aleph zero. Your objection fails. Moreover, you’ve ignored my second point (about accepting absurdities such as Hilbert’s Hotel and a library with an infinite number of books in the real world).
I will, however, share some of Craig’s own comments on similar issues in his excellent article “The Kalam Cosmological Argument” in the Blackwell Companion to Natural Theology:
*Sometimes it is said that we can find concrete counterexamples to the claim that an actually infinite number of things cannot exist, so that Premise (2.11) must be false. For example, Walter Sinnott-Armstrong asserts that the continuity of space and time entails the existence of an actually infinite number of points and instants (Craig & Sinnott- Armstrong 2003, p. 43). This familiar objection gratuitously assumes that space and time are composed of real points and instants, which has never been proven. Mathematically, the objection can be met by distinguishing a potential infinite from an actual infinite. While one can continue indefinitely to divide conceptually any distance, the series of subintervals thereby generated is merely potentially infinite, in that infinity serves as a limit that one endlessly approaches but never reaches. This is the thoroughgoing Aristotelian position on the infinite: only the potential infinite exists. This position does not imply that minimal time atoms, or chronons, exist. Rather time, like space, is infinitely divisible in the sense that division can proceed indefinitely, but time is never actually infinitely divided, neither does one arrive at an instantaneous point. If one thinks of a geometrical line as logically prior to any points which one may care to specify on it rather than as a construction built up out of points (itself a paradoxical notion13), then one’s ability to specify certain points, like the halfway point along a certain distance, does not imply that such points actually exist independently of our specification of them. As Grünbaum emphasizes, it is not infi- nite divisibility as such which gives rise to Zeno’s paradoxes; the paradoxes presuppose the postulation of an actual infinity of points ab initio. “. . . [A]ny attribution of (infinite) ‘divisibility’ to a Cantorian line must be based on the fact that ab initio that line and the intervals are already ‘divided’ into an actual dense infinity of point-elements of which the line (interval) is the aggregate. Accordingly, the Cantorian line can be said to be already actually infinitely divided” (Grünbaum 1973, p. 169). By contrast, if we think of the line as logically prior to any points designated on it, then it is not an ordered aggregate of points nor actually infinitely divided. Time as duration is then logically prior to the (potentially infinite) divisions we make of it. Specified instants are not temporal intervals but merely the boundary points of intervals, which are always nonzero in duration. If one simply assumes that any distance is already composed out of an actually infinite number of points, then one is begging the question. The objector is assuming what he is supposed to prove, namely that there is a clear counterexample to the claim that an actually infinite number of things cannot exist.
Some critics have charged that the Aristotelian position that only potential, but no actual, infinites exist in reality is incoherent because a potential infinite presupposes an actual infinite. For example, Rudy Rucker claims that there must be a “definite class of possibilities,” which is actually infinite in order for the mathematical intuitionist to regard the natural number series as potentially infinite through repetition of certain mathematical operations (Rucker 1980, p. 66). Similarly, Richard Sorabji asserts that Aristotle’s view of the potentially infinite divisibility of a line entails that there is an actually infinite number of positions at which the line could be divided (Sorabji 1983, pp. 210–3, 322–4).*
If this line of argument were successful, it would, indeed, be a tour de force since it would show mathematical thought from Aristotle to Gauss to be not merely mistaken or incom- plete but incoherent in this respect. But the objection is not successful. For the claim that a physical distance is, say, potentially infinitely divisible does not entail that the distance is potentially divisible here and here and here and. . . . Potential infinite divisibility (the prop- erty of being susceptible of division without end) does not entail actual infinite divisibility (the property of being composed of an infinite number of points where divisions can be made). The argument that it does is guilty of a modal operator shift, inferring from the true claim
(1) Possibly, there is some point at which x is divided
to the disputed claim
(2) There is some point at which x is possibly divided.
(to be continued)