"Our great democracies still tend to think that a stupid man is more likely to be honest than a clever man." - Bertrand Russell
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"Traditional moral theology distinguished between synderesis and syneidesis, claiming that these two terms and ideas were to be found in Scripture itself. By synderesis they understood the habit of conscience, the basic sense of responsibility that characterizes the human person. And by syneidesis they understood the act of conscience, the judgment by which we evaluate a particular action. .. . The term syneidesis is clearly present in Scripture. But what of synderesis? The simple and embarrassing fact is that this term does not appear in Scripture. Indeed, there is no such word in the Greek language. Rather, it appears that this entire theological tradition is the result of a massive error.
As nearly as we can tell, it was St. Jerome who first alleged the existence of these two different words for conscience. In preparing the first Latin text of the Bible, Jerome was apparently working from a Greek manuscript that was not altogether legible. He had to deal with sections where the topic was clearly conscience but the word did not appear to be “syneidesis” but rather “synderesis.” Jerome studied the text and thought he detected differing nuances when one or the other word was used. Thus he concluded that the latter must simply be a Greek word with which he was unfamiliar, a word being used to make a veiy specific point. But recent scholarship has made clear that Jerome was wrong. There are not two words in Greek for conscience, but only one."
--- An Understanding of Conscience / Timothy E. O'Connell