Litotes affirms something by denying its opposite — not unreasonable, no small achievement, not a bad result. The double negative arrives at a positive, but not quite the same positive that stating it directly would have reached.
The gap between the two is where the device operates.
From Acts, in the King James translation, Paul identifying himself: “a citizen of no mean city.” He means Tarsus was significant. Saying so by denying the opposite claims the point while appearing to decline to boast.
Litotes is a specific form of understatement. The distinguishing feature is the negation: understatement minimises, litotes negates the opposite.
Litotes does two things at once, and they pull in opposite directions. It asserts the positive, and it signals restraint in asserting it. The speaker gets credit for modesty while the claim lands anyway, which is why the figure is so common in academic and diplomatic prose, where overt confidence is penalised.
It is also genuinely useful for precision. “Not unhelpful” is not a synonym for “helpful”; it occupies a narrower band, somewhere above neutral and short of endorsement. A writer who means that band has no better way to say it.
The hazard is that the same vagueness can be deployed deliberately. “The results are not inconsistent with our hypothesis” is a sentence that has carefully not claimed the results support anything, while sounding as though it has. In technical writing especially, a run of litotes is worth translating into direct statements to see what is actually being asserted — the answer is sometimes very little.
