Solus Christus was one of the five Latin phrases (Five Solas) which came out from the Protestant Reformation as the basic essentials of Christian belief. Much like the Reformation itself, the Solas stood in distinction from many of the teachings of the Roman Catholic Church. With respect to Solus Christus, the specific point was that it is only “Christ alone” who is mediator between God and man – only through Him may we have access to the Father.
The disciples were troubled at Jesus’ prediction of betrayal and what would come as a result of it. Jesus, comforting them, explains that He will go to prepare a place and they knew the way to get there. Thomas answered in a manner, however, as if perplexed, asking how they could possibly know the way if they didn’t even know the destination, to which Jesus explains, “I am the way and the truth and the life. No one comes to the Father except through me” (Jn 14:6). This is the point of the phrase itself: Jesus is sole mediator and there is no one else through which we must go for reconciliation to the Father. God gave His only begotten Son to ransom the lost from the penalty of sin, if they would only trust in Him alone, and this was His great pleasure (Jn 3:16-17; Eph. 1:8-10).
Through the Scripture (Sola Scriptura), we read that we are saved by faith (Sola Fide) in Christ Jesus alone (Solus Christus) through grace (Sola Gratia) to the glory of God (Soli Deo Gloria).