Cicero about paragraph marks

Question

I have looked on the Internet about books with no punctuation marks and found a post by Thomas Musselman at Quora:

Punctuation is a post-3rd Century invention so when you read older texts you are reading them with someone sticking in punctuation that didn’t exist when the writer wrote it or his first readers read it. Cicero, e.g., hated marks showing paragraph changes. Purists thought you just should know when to break (from practice reading the text and reading aloud).

Does anybody know where to read the respective passage by Cicero?

2022-06-13: Now answered on Philosophy.StackExchange: q/99837

Answer 1

While this was answered on Philosophy.SE, that answer doesn't provide an English translation. So let's add one here.

This comes from Cicero's Orator (note: not his more famous De Oratore), section 228:

quae non aut spiritu pronuntiantis aut interductu librari sed numero coacta debet insistere, verum etiam quod multo maiorem habent apta vim quam soluta.

[Your paragraph] which ought to end, not because of the breath of the speaker [running out] or because of a copyist's punctuation, but indeed, because well-tightened [paragraphs] have much greater force than loose ones.

Translation mine. ("Paragraph" here is a somewhat loose translation; you could also translate it as "sentence". What's important is that it's a subsection of your speech.) In other words, you shouldn't be relying on punctuation to tell you when to take a break, and you shouldn't be running out of breath; you should put breaks where they're most effective for the rhetoric.