That they may be one – Ut unum sint has been the rallying cry of Churchmen since Vatican II, and the explanation for the promotion of an ecumenical agenda that places unity before everything. But what is the nature of the unity for which the Lord prayed His heavenly Father on the way to Gethsemane? Indeed, most Catholics cannot answer with precision what exactly the Church is, the conditions for belonging to it, or its necessity for salvation. If you want a clear and concise explanation of these principles, Satis Cognitum is the place to begin.