For the Catholic Church, “Sacred Scripture” is one of two pillars of faith, the other being “Sacred Tradition”. As we have already seen, the Catholic Church views the two “with equal sentiments of devotion and reverence” or, in more prosaic terms, as having equal weight and importance. In practice, Tradition and Scripture work together, always complementary and never in opposition to one another, to underpin Catholic teaching. But the Catholic recognition of the weight of Tradition has been labelled a “fatal error” by some Protestants.
So what exactly is Tradition? The capital ‘T’ is helpful, for the term is a technical one that signifies much more than just the “traditions” – for example the liturgical practices of particular groups of Catholics at particular times – that may be altered over the years. In Tradition, by contrast, we find part of the unalterable, essential teaching of the Church. The Church teaches that the "Sacred deposit" of the faith was entrusted to her by the apostles, and that it was and is expressed both in Scripture and Tradition (CCC 84). Both Scripture and Tradition flow “from the same divine wellspring” (Dei Verbum, para. 9).