2.5. What is heresy, and how is it different from error?

Heresy is the obstinate denial or doubt, after baptism, of a truth that must be believed with divine and Catholic faith (Canon 1325, 1917 Code). It involves direct rejection of revealed truth—i.e., dogma.

Error, on the other hand, may involve mistaken ideas or false theological opinions. It may be due to ignorance or confusion and does not necessarily concern defined dogma.

Heresy is far more serious because it destroys the supernatural virtue of faith and separates one from the Church.