The fall and original sin
The doctrine of original sin describes humanity’s wounded condition and need for redemption. It distinguishes the first human disobedience from the condition inherited by later generations, which is not a personal act committed by each newborn. Human nature remains good but wounded. Sin is neither an unavoidable excuse for wrongdoing nor the final word about human destiny; grace opens the way to healing.
Follow the sources
An original library introduction, with sources for further study. This is a starting point rather than a complete treatment or a finished formation lesson.