There are two ways of looking at this.
1- The obvious way: We define Catholicism/Christianity as the visible Church. It is obvious from the Bible that God has given parts of His truth to those outside the Church (such as Cornelius in Acts or the law written on our hearts).
2- The weird, technical way: Those portions of the truth found outside the visible Church are joined to the invisible Church. All truth is in the Church the Body of Christ but some of it is experienced outside the visible community of the Church.