Is it true, that natural virtue -the cardinal virtues, are supplied by grace after the fall of Adam since most people would not then be interested in being virtuous?
From the Catechism:
1804 Human virtues are firm attitudes, stable dispositions, habitual perfections of intellect and will that govern our actions, order our passions, and guide our conduct according to reason and faith. They make possible ease, self-mastery, and joy in leading a morally good life. The virtuous man is he who freely practices the good.
The moral virtues are acquired by human effort. They are the fruit and seed of morally good acts; they dispose all the powers of the human being for communion with divine love.
1810 Human virtues acquired by education, by deliberate acts and by a perseverance ever-renewed in repeated efforts are purified and elevated by divine grace. With God’s help, they forge character and give facility in the practice of the good. The virtuous man is happy to practice them.
1811 It is not easy for man, wounded by sin, to maintain moral balance. Christ’s gift of salvation offers us the grace necessary to persevere in the pursuit of the virtues. Everyone should always ask for this grace of light and strength, frequent the sacraments, cooperate with the Holy Spirit, and follow his calls to love what is good and shun evil.
just like 1ke said, this is not the understanding of the catholic church. Saving grace comes from God alone, and not of men or our actions, but what justifies us and prepares us to receive that grace are faith and our performance of the good works for which we have been ordained in Christ. (eph 2:10)
In catholicism, we are called to imitate God’s perfection, and this includes striving to develop our own intrinsic virtue. God does not want sheep, He wants us to be hearty warriors of the faith.