Solus Christus in a very easy way to define and comprehend that Christ Alone is the only Mediator and Saviour between God and man without negating His divinity. It is differentiated from Soli Deo Gloria because its main thrust is of Christ as mediator and not in contrasting Him with the other members of the Godhead.
In John 5:39 Jesus states:
” You search the Scriptures because you think that in them you have eternal life; it is these that testify about Me”
This was not the rantings of a delusional 1st Century Carpenter with an over-inflated ego: But rather was the great I AM speaking to those around Him living in unbelief and declaring that HE is Who He is. This was Jesus Christ affirming that HE is the way of eternal life and that the Scriptures (Sola Scriptura) testified of where that Life could be found.
We can look around us using the faculties that God has given us to determine that there is a Creator. It is an unmistakable, undeniabe, and self-attesting attribute of the Glory of God that there is a creation to behold and that He is active in it. Yet we cannot know God, or better yet, Him as Father without the work of Jesus Christ and His substitutionary death on the cross. John Calvin in the Institutes of the Christian Religion declared:
” The Knowledge of God as Creator is of no avail without faith in Christ the Redeemer. For although God is still Pleased in many ways to manifest his paternal favour towards us, we cannot, from a mere survey of the world, infer that He is Father. “
We have already seen where salvation is by grace alone (sola gratia) through faith alone (sola fide) and now we are looking at WHO is the Mediator of that salvation to sinful man. It is His sufficiency that declares our insufficiency, His sinless life that is the ransom for our sinful existence, and His atonement is the means of justification and reconciliation to the Father. No merit of men, nor treasury of the saints, no works of ours performed in the here and now or in purgatory can add to this work. It is Christ Alone, Solus Christus, who has paved the road back to the Father using His precious body as the stones and His blood to mix the mortar that binds us to him.
This claim of ours that Christ Alone is Mediator seems intolerant and unjust but to be true to the Scriptures we must aver what is found therein: That Christ is the exclusive Saviour given unto men. We must have faith in Christ to avoid condemnation ( John 3:18 ), to know that Christ is the way to the Father (John 14:1-6), His name is the only name given whereby we must be saved ( Acts 4:12 ), and this salvation is mediated by Christ Himself ( 1 Timothy 2:5-6 ).
The times of ignorance have long passed: