Ternio sacrorum theorematum, de uno Deo, de uno mediatore, et de Iesu, qui est Christus

are common notions to us.
Whatever is true for all believers on account of the testimony of the Holy Spirit, that is most certain.
It deservedly seems true to all believers that Christ is one: because the 4 axioms provided above are known to them.
The second demonstration of the same kind.
The Father has blessed us in only one: as Axiom 6 teaches.
He blessed us in one Christ. The argument is that in this one he chose us, called us, justified us, and will glorify us.
The third demonstration, drawn from the consideration of both Adams. 1 Cor. 15:47 & seq.
The consequences of contraries are contrary.
Yet that Terrestrial Adam, through whom sin entered into the world, and through sin death, is one in number: and so death passed into all men, in whom all have sinned. Rom. 5:12.
The fourth demonstration, from the definition of the subsumed.
There is only one theanthropos God-man person, a mediator, etc., as the first two axioms advise.
Lord Jesus is that person: as is clear from the definition.

Analytical Demonstrations.
The first, drawn from effects and proper signs.
The anakephalaiōsis recapitulation/summing up of the whole Catholic Church occurred in no one but one. Therefore he is said to be the one Lord of all, through whom are all things, and we through him: as the first axiom testifies.
But in Christ Jesus that anakephalaiōsis was accomplished. For we have been gathered together in summary, so that in the one Lord Jesus (who is our head, and of whose living members we are) associated by the link of the Holy Spirit, we might be saved by him from wrath. This is what Axiom 4 means.