It is impossible to make people understand their ignorance, for it requires knowledge to perceive it and, therefore, he that can perceive it hath it not.

Taylor’s remark turns on a paradox about self-knowledge: recognizing one’s ignorance is itself a kind of knowledge. People who lack the intellectual tools to judge a subject also lack the capacity to see the limits of their understanding, so exhortations or explanations may not penetrate. The line anticipates later discussions of “meta-knowledge” (knowing what one does not know) and the social difficulty of correcting confident error. It also carries a moral edge typical of Taylor’s devotional prose: humility is not merely a virtue but an epistemic achievement, and those most certain may be least qualified to assess themselves.