Heresy consists in the formal denial or doubt by a baptized person of any revealed truth of the Catholic Faith; as a crime it consists of the outward and pertinacious manifestation of the sin. As we can see below, Scripture speaks frequently of heresy entering the Church. We can also see that heresy is possible even with a Pope. In that case, the Pope is immediately ejected from the Church and papal infallibility no longer applies. See quotes below. References to Heresy in Scripture: Take heed to yourselves, and to the whole flock, wherein the Holy Ghost hath placed you...