Meaning of sentence from "A Tale of Two Cities"?

Question

> Reins and whip and coachman and guard, however, in combination, **had read that article of war which forbade a purpose** otherwise strongly in favour of the argument, that some brute animals are endued with Reason; and the team had capitulated and returned to their duty. What does this mean? (Bolding my own.)

Answer 1

The super-short version is:

The coachman kept whipping the horses to go faster.

The way Dickens is writing it is something like:

The coachman and his whip believed in the doctrine that denied the idea that animals could think, and the horses gave in and did what he wanted.

Basically he's saying that the coachman is whipping them so ferociously that he could only do it if he was committed to the idea that the horses were too dumb to suffer.