We have not as yet in our podcast gone through Cicero's On Fate. If we do, here is one passage we will want to focus on. Here, Cicero criticizes Epicurus' view of the swerve as unnecessary. But Cicero also explains the importance of the question, and in contrast to what we might expect, Cicero takes the side of Carneades. Carneades (an Academic Skeptic) joins with Epicurus in result (but not in reasoning). He attacks the Stoic view of hard determinism/fate based on non-swerve grounds.
This is the Long & Sedley translation from The Hellenistic Philosophers:
Cicero, On Fate 21-25
At this initial stage, if I were disposed to agree with Epicurus and to deny that every proposition is either true or false, I would rather accept that blow than allow that all things happen through fate. For the former view is at least arguable, whereas the latter is truly intolerable. Chrysippus, then, strains every nerve to persuade us that every axioma (proposition) is either true or false. For just as Epicurus is afraid that if he admits this he will have to admit that all events happen through fate — for if one of the two has been true from all eternity it is certain, and if certain then necessary too, which he considers enough to prove both necessity and fate - so too Chrysippus fears that if he fails to secure the result that every proposition is either true or false he cannot maintain that everything happens through fate and from eternal causes of future events. But Epicurus thinks that the necessity of fate is avoided by the swerve of atoms. Thus a third type of motion arises in addition to weight and impact, when the atom swerves by a minimal interval, or elachiston as he terms it.
That this swerve occurs without a cause he is forced to admit in practice, even if not in so many words. For it is not through the impact of another atom that an atom swerves. How, after all, can one be struck by another if atomic bodies travel perpendicularly in straight lines through their own weight, as Epicurus holds? For it follows that one is never driven from its course by another, if one is not even touched by another. The consequence is that, even supposing that the atom does exist and that it swerves, it swerves without a cause. Epicurus' reason for introducing this theory was his fear that, if the atom's motion was always the result of natural and necessary weight, we would have no freedom, since the mind would be moved in whatever way it was compelled by the motion of atoms. Democritus, the originator of atoms, preferred to accept this consequence that everything happens through necessity than to rob the atomic bodies of their natural motions. A more penetrating line was taken by Carneades, who showed that the Epicureans could defend their case without this fictitious swerve. For since they taught that a certain voluntary motion of the mind was possible, a defence of that doctrine was preferable to introducing the swerve, especially as they could not discover its cause.
And by defending it they could easily stand up to Chrysippus, for by conceding that there is no motion without cause they would not be conceding that all events were the result of antecedent causes. For our volition has no external antecedent causes. Hence when we say that someone wants or does not want something without a cause, we are taking advantage of a common linguistic convention: by 'without a cause' we mean without an external antecedent cause, not without some kind of cause, just as, when we call a jar 'empty', we are not speaking like natural philosophers who hold the empty (void) to be absolute nothing, but in such a way as to say that the jar is, for example, without water, without wine or without oil, so too when we say that the mind moves 'without a cause' we mean without an external antecedent cause, not entirely without a cause. Of the atom itself it can be said that, when it moves through the void as a result of its heaviness and weight, it moves without a cause, in as much as there is no additional cause from outside. But here too, if we don't all want to incur the scorn of the natural philosophers for saying that something happens without a cause, we must make a distinction and say as follows: that it is the atom's own nature to move as a result of weight and heaviness, and that that nature is itself the cause of its moving in that way. Similarly for voluntary motions of the mind there is no need to seek an external cause. For a voluntary motion itself has it as its own intrinsic nature that it should be in our power to obey us. And this fact is not without a cause: for the cause is that thing's own nature.