Infallibility has nothing whatsoever to do with sin. All human beings sin, and the Pope is a human being. A few popes over the ages have led pretty immoral personal lives. Papal infallibility is the result of the promises Jesus Christ made to the first Pope - "Whatsoever you bind upon Earth is bound in Heaven", and "The Holy Spirit will guide you into all truth", and "He who hears you hears Me". These promises guarantee that The Pope cannot be wrong when officially stating a matter of doctrine or morality. It is this divine guarantee that assures that members of the Church Jesus Christ founded will always have access to full and complete truth. Which is why it remains one in belief, one in teaching, one in worship, one in biblical understanding after 2,000 years. The Pope can make errors on financial matters, what team will win the World Series, the weather, and any number of other subjects, just like the rest of us. The doctrinal chaos of Protestantism demonstrates what happens when people abandon Jesus Christ's Church, which He said was to remain one, and its divine promises, and attempt to find truth any other way. Thousands of conflicting manmade denominations, each claiming to be taking truth from "the Bible alone", yet the teaching of each denomination contradicting the teaching of the others, all within a few hundred years.