As
@prodromos said, we did not claim that - he used a Hebrew and Aramaic source which is no longer extant, with one exception, that being the Psalter, which he did translate from the Septuagint as the Roman Church, like the Orthodox Church, was dependent on Septuagint versification for their use of the Psalter. So consequently, if you compare the Challoner Douai Rheims Psalter with a Septuagint-based psalter of the same vintage, such as the Lancelot Brenton Psalter, or a newer Septuagint-derived Psalter, such as the Jordanville Psalter or the Psalter According to the Seventy from Holy Transfiguration Monastery, you will find that they align on chapter and verse boundaries and the content of certain distinctive readings, such as Psalm 95:5 (which is a much better reading than Masoretic Psalms 96:5 ; we already know the gods of the gentiles are idols, but the Septuagint provides us with some greatly more useful information by telling us “the gods of the gentiles are demons,” which explains the darker and more disturbing aspects of various ancient pagan religions such as human sacrifice, and the extreme darkness and evil that we see today, in much of Hinduism and Buddhism and in the fragments of the Latin pagan religion, such as the indigenous Inca religion, which is still practiced and involves the tragic sacrifice of beautiful and immensely intelligent llamas and alpacas, and the vile Santa Muerte death cult in Mexico, which by the way is not endorsed by the RCC even now.