Newman, on knowing what you are talking about

MANY a disciple of a philosophical school, who talks fluently, does but assert, when he seems to assent to the dicta of his master, little as he may be aware of it. Nor is he secured against this self-deception by knowing the arguments on which those dicta rest, for he may learn the arguments by heart, as a careless schoolboy gets up his Euclid. This practice of asserting simply on authority, with the pretence and without the reality of assent, is what is meant by formalism. To say "I do not understand a proposition, but I accept it on authority," is not formalism; it is not a direct assent to the proposition, still it is an assent to the authority which enunciates it; but what I here speak of is professing to understand without understanding. It is thus that political and religious watchwords are created; first one man of name and then another adopts them, till their use becomes popular, and then every one professes them, because every one else does. Such words are "liberality," "progress," "light," "civilization;" such are "justification by faith only," "vital religion." "private judgment," "the Bible, and nothing but the Bible." Such, again, are "Rationalism," "Gallicanism," "Jesuitism," "Ultramontanism"—all of which, in the mouths of conscientious thinkers, have a definite meaning, but are used by the multitude as war-cries, nicknames, and shibboleths, with scarcely enough of the scantiest grammatical apprehension of them to allow of their being considered really more than assertions. (Grammar of Assent, pt I, 4, § 1)