Q. 2. Is this doctrine of the Trinity, then; a fundamental article, upon the belief of which our salvation depends?
A. Beyond all doubt it is: because without the knowledge and belief of the Trinity of persons, we would remain ignorant of the love of the Father, the merit of the Son, and the sanctifying influences of the Holy Ghost, in the purchase and application of redemption; without which there could be no salvation, John 17:3, -- "This is life eternal, that they might know thee the only true God, and Jesus Christ whom thou hast sent." James Fisher; Catechism on the Catechism, Q. 6
Does Fisher overstate his case here? Tertullian and Origen, for example, had erroneous 'knowledge' of the Trinity. He can't mean 'perfect' knowledge so what does he mean?