Passage (John Stuart Mill, *On Liberty*, 1859, Ch. II, continued): "For while every one well knows himself to be fallible, few think it necessary to take any precautions against their own fallibility, or admit the supposition that any opinion, of which they feel very certain, may be one of the examples of the error to which they acknowledge themselves to be liable. Absolute princes, or others who are accustomed to unlimited deference, usually feel this complete confidence in their own opinions on nearly all subjects. People more happily situated, who sometimes hear their opinions disputed, and are not wholly unused to be set right when they are wrong, place the same unbounded reliance only on such of their opinions as are shared by all who surround them, or to whom they habitually defer: for in proportion to a man's want of confidence in his own solitary judgment, does he usually repose, with implicit trust, on the infallibility of 'the world' in general. And the world, to each individual, means the part of it with which he comes in contact; his party, his sect, his church, his class of society." What is the function of the qualifier 'in proportion to' in the sentence about a man's want of confidence in his own solitary judgment?