What follows is a quote by Charles Morgridge from a discourse he gave in 1837. ...
"Promises of salvation are expressly made to all who embrace the gospel as it is defined by Christ and the Apostles. But no promise is made to the Trinitarian as such. There is no scripture which asserts that whosoever believes in the Trinity, or in the two natures, or in the Son's equality with the Father ... shall be saved. Nor does any scripture assert that whosoever believeth not these doctrines shall be damned. But if no promise is made to him who embraces the gospel as it is defined by Trinitarians, and no threatening against him who does not embrace it as thus defined, is not this sufficient evidence that their definitions are not correct?
All who believe on Jesus Christ, as the Son of God, have assurance from Christ himself, of everlasting life. All who do not believe Jesus to be the Son of God, are assured, by the same authority, that they shall not see life, but the wrath of God abideth on them.
What, then, does the true believer gain by admitting the doctrine of the Trinity? If it does not secure to him a single promise, nor shield him from a single threatening, or what use can it possibly be to him? It cannot make one hair either white or black."