Our Lord said: "Not every one that saith to me, Lord, Lord, shall enter into the kingdom of heaven..."
Fr. Wathen explains...
"… concerning those who are not in the Catholics Church, by what power will they be saved? Let us grant that they cannot save themselves anymore than any man can go to the moon without some kind of help.
The power of salvation comes from Christ Himself, as Christ said, without Me you can do nothing. When He said without me you can do nothing, He meant literally nothing. You cannot take that first step without Christ.
And you will say; well they believe in Christ, and my answer is; you forget that Christ and the Church are one. If you separate the Church from Christ, you have sought to divide Christ. There is no such thing as Christ without the Church because the Church is His Mystical Body.
As St Augustine referred to this mystery, the Church is with Christ, the whole Christ, there is no salvation independently of the Church, anymore than there is salvation independently of Christ. You can never separate Christ from the Church because the two are one. And this is of course the great heresy of Protestantism, they dare to separate salvation from Christ because they separate salvation from the Church...."