Catechism of the Catholic Church §164 — excerpt
Now, however, "we walk by faith, not by sight"; we perceive God as "in a mirror, dimly" and only "in part". Even though enlightened by him in whom it believes, faith is often lived in darkness and can be put to the test.
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.