He makes the common mistake these days of calling these people, students.  Students are ones who study but there is no evidence these people he speaks of, although paying fees at a university or employed by one, actually do study or have in the past studied.  
    In the case of any person whose judgement is really deserving of confidence, how has it become so?  Because he has kept his mind open to criticism of his opinion and conduct.   Because it has been his practice to listen to all that could be said against him; to profit by as much of it as was just, and expound to himself, and on occasion to others, the fallacy of what was fallacious.  Because he has felt that the only way in which a human being can make some approach to knowing the whole of a subject, is by hearing what can be said about it by persons of every variety of opinion, and studying al mode in which it can be looked at by every variety of mind.   No wise man ever acquired his wisdom in any mode but this; nor is it the nature of human intellect to become wise in any other manner”  John Stuart Mill. On Liberty, Chapter II.