I am reading a book about Aristotle. Aristotle lays out a potential argument against infinite divisibility by the Atomists, that infinite division would leave components of zero-magnitude which could not sum to the origin whole. In response, he differentiates actual and potential infinities, with a potential infinity simply meaning "endlessly divisible". Then he attempts to improve this argument, and this is where I'm at a loss. Here is the relevant passage:
He offers a distinction between different kinds of potentiality. A block of marble has the potentiality to become a statue: when this is realized, the statue will be there, all of it at once. But the parts into which a temporal period or series can be divided have a different kind of potentiality. They cannot be all there at once: when I wake up, the day ahead contains both morning and afternoon, but they cannot both occur at once.
(from Anthony Kenny's A New History of Western Philosophy: Ancient Philosophy, p. 181)
The author goes on to say this is the basis of a further argument against the Atomists, and that it is fallacious arguing erroneously from "if p or q are possible, p and q are possible". It isn't clear to me how this distinction could serve as an argument against Atomism or in defense of infinite divisbility, nor how it resembles this fallacious form.