To be conscious that you are ignorant of the facts is a great step to knowledge.
Benjamin Disraeli
As St. Maximos has said, "To think that one knows prevents one from advancing in knowledge." St. John Chrysostom points out that there is an ignorance which is praiseworthy: it consists in knowing consciously that one knows nothing. In addition, there is a form of ignorance that is worse than any other: not to know that one does not know. Similarly, there is a knowledge that is falsely so called, which occurs when, as St. Paul says, one thinks that one knows but does not know (see I Corinthians 8:2).
St. Peter of Damaskos,"The Four Virtues of the Soul", from G. E. H. Palmer, Philip Sherrard, and Bishop Kallistos Ware, "The Philokalia: Vol. III," (London: Faber and Faber, 1984), pp. 100 - 101