Catechism of the Catholic Church §37 — excerpt
In the historical conditions in which he finds himself, however, man experiences many difficulties in coming to know God by the light of reason alone:
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Also cites: Pius XII, Humani generis 561: DS 3875