Catechism of the Catholic Church

Catechism translations

37 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: Though human reason is, strictly speaking, truly capable by its own natural power and light of attaining to a true and certain knowledge of the one personal God, who watches over and controls the world by his providence, and of the natural law written in our hearts by the Creator; yet there are many obstacles which prevent reason from the effective and fruitful use of this inborn faculty. For the truths that concern the relations between God and man wholly transcend the visible order of things, and, if they are translated into human action and influence it, they call for self-surrender and abnegation. The human mind, in its turn, is hampered in the attaining of such truths, not only by the impact of the senses and the imagination, but also by disordered appetites which are the consequences of original sin. So it happens that men in such matters easily persuade themselves that what they would not like to be true is false or at least doubtful.

Translation God can be understood by reason yet reason has obstacles to that understanding of God The relation between God and man goes beyond what can be observed ("visible order of things") if they can be part of man's experience, man must submit to God ("they call for self-surrender and abnegation") Man's reason ("the human mind") cannot easily attain "such truths" "impacted" (hampered) by senses (what man imperfectly perceives) and imagination (what man imagines or dreams of) "disordered" (negatively impacted by) "appetites" (desires) that "are the consequences of original sin." so when man false short of pure reason (incorrect perception, sin, etc.) they convince ("easily persuade") themselves that what they don't want to be true (God's word) is not true, or "doubtful" (likely not true)