A man who never becomes fit for more than an assistant's duty should remain an assistant all his life, and his juniors should be promoted over him.
 John Stuart Mill, Considerations on Representative Government (1861). copy citation

Context

“Even the inferior in qualifications among such a corps of functionaries consisted, it must be remembered, of men who had been brought up to their duties, and had fulfilled them for many years, at lowest without disgrace, under the eye and authority of a superior. But, though this diminished the evil, it was nevertheless considerable. A man who never becomes fit for more than an assistant's duty should remain an assistant all his life, and his juniors should be promoted over him. With this exception, I am not aware of any real defect in the old system of Indian appointments. It had already received the greatest other improvement it was susceptible of, the choice of the original candidates by competitive examination, which, besides the advantage of recruiting from a higher grade of industry and capacity, has the recommendation that under it, unless by accident, there are no personal ties between the candidates for offices and those who have a voice in conferring them.” source