Can someone explain this?

The Catholic Church sees merit in examining what it calls Partial Agnosticism, specifically those systems that "do not aim at constructing a complete philosophy of the Unknowable, but at excluding special kinds of truth, notably religious, from the domain of knowledge." However, the Church is historically opposed to a full denial of the ability of human reason to know God. The Council of the Vatican, relying on biblical scripture, declares that "God, the beginning and end of all, can, by the natural light of human reason, be known with certainty from the works of creation" (Const. De Fide, II, De Rev.)