Ignorance implies a defect in the mind, even about any particular things whatever, so that it is contrary to knowledge, which gives man a right judgment about particular causes, viz. about creatures.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic ignorance judgment
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/18755/pg18755-images.html

Context

“Hence it is dulness of mind that renders the mind unable to pierce into the heart of a thing. A man is said to be a fool if he judges wrongly about the common end of life, wherefore folly is properly opposed to wisdom, which makes us judge aright about the universal cause. Ignorance implies a defect in the mind, even about any particular things whatever, so that it is contrary to knowledge, which gives man a right judgment about particular causes, viz. about creatures. Rashness is clearly opposed to counsel, whereby man does not proceed to action before deliberating with his reason. Reply Obj. 2: The gift of understanding is about the first principles of that knowledge which is conferred by grace;” source