Karl Adam on subjective doubt

"The Church's claim to the truth is so deeply set in the hard granite of historical facts and of logical consistency, and is so intimately bound-up with the ultimate and profoundest requirements of conscience, with its reverence before that which is holy and divine, that it can stand fast and prevail over any possible inquiry, whether past, present or future. Moreover the Catholic cannot become the prey of any merely subjective doubt, resting upon false presuppositions or erroneous deductions, so long as he does not proudly and arrogantly exclude that light of grace which is refused to no man of good will.

This light will always be clear and strong enough to reveal the sources of any misunderstanding and to prevent him sinking into invincible error (error invincibilis). The Catholic is therefore generally protected from that radical attitude which deliberately detaches a man inwardly from the professed faith of Catholic Christianity and, reveling in a purely negative criticism, embarks upon research about Christ and the Church as though neither existed. On the other hand the Church does not compel the Catholic to shut his eyes to the religious problems which arise, nor conviction of conscience. Even though the judgment of his conscience be objectively false and even though it be not in its genesis ethically irreproachable, yet he is bound to follow conscience and conscience alone."