There is a certain measure of faith to which all are obliged, and which is sufficient for the simple (simplicibus) and perhaps for all laymen—that is, every adult must believe that God exists and that He rewards all good people. He must also believe in the other articles of the Creed implicitly (implicite), that is, he must believe that whatever the Catholic Church believes is true…
…
Such is the power of implicit faith that there are those who say that if someone has it—that is, he believes in everything the Church believes—but his natural reason (ratione naturali) makes him hold the erroneous opinion that the Father is greater than the Son or precedes Him in time, or that the three persons are separate beings, he is neither a heretic nor a sinner, so long as he does not defend his error and so long as he believes that this is the faith of the Church. In that case, the faith of the Church replaces his opinion, since, though his opinion is false, it is not his faith, rather his faith is the faith of the Church.