Doctrine of the Mean
The Four Books of Confucianism give some insightful explanations of "de" "virtue". Note that the following quotations cite Charles Muller's scholarly translations of the "Analects", "Doctrine of the Mean", "Great Learning", and "Mencius". The more familiar translations of James Legge render "ren" "humaneness; human-heartedness" as "perfect virtue", which occasionally creates confusion with "de" as "virtue". Compare their translations of these two "Analects" passages.