Marcus Grodi and Msgr. Jeffrey Steenson continue through Book 3 of Against Heresies by discussing what St. Irenaeus of Lyons had to say about the importance of preserving the deposit of faith.

Writing in the 2nd century, St. Irenaeus points out that the errors faced by the Church in his time were easily traceable to key figures at key times, who brought their new and controversial ideas to Christianity.

By contrast, the faith of the Church can be traced to Jesus Christ himself, and the successors of the apostles are charged to guard that faith against error until His return.