Saint Peter Of Damascus
There are four forms of wisdom: first, moral judgment, or the knowledge of what should and should not be done, combined with watchfulness of the intellect; second, self-restraint, whereby our moral purpose is safeguarded and kept free from all acts, thoughts and words that do not accord with God; third, courage, or strength and endurance in sufferings, trials and temptations encountered on the spiritual path; and fourth, justice, which consists in maintaining a proper balance between the first three. These four general virtues arise from the three powers of the soul in the following manner: from the intelligence, or intellect, come moral judgment and justice, or discrimination; from the desiring power comes self-restraint; and from the incensive power comes courage.
Each virtue lies between the unnatural passions. Moral judgment lies between craftiness and thoughtlessness; self-restraint, between obduracy and licentiousness; courage, between overbearingness and cowardice; justice between over-frugality and greed. The four virtues constitute an image of the heavenly man, while the eight unnatural passions constitute an image of the earthly man (see I Corinthians 15:49).
God possesses a perfect knowledge of all these things, just as He knows the past, the present and the future; and they are known to some extent by him who through grace has learned from God about His works, and who through this grace has been enabled to realize in himself that which is according to God's image and likeness (see Genesis 1:26). But if someone claims that, simply by hearing about these things, he knows them as he should, he is a liar. Man's intellect can never rise to heaven without God as a guide; and it cannot speak of what it has not seen, but must first ascend and see it. On the level of hearsay, you should speak only of things that you have learned from the Scriptures, and then with circumspection, confessing your faith in the Father of the Logos, as St. Basil the Great puts it, and not imagining that through hearsay you possess spiritual knowledge; for that is to be worse than ignorant. 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).
from G. E. H. Palmer, Philip Sherrard, and Bishop Kallistos Ware, "The Philokalia: vol. III," (London: Faber and Faber, 1984), pp. 100 - 101