“I answer that, Two things are requisite for faith. First, that the things which are of faith should be proposed to man: this is necessary in order that man believe anything explicitly.
The second thing requisite for faith is the assent of the believer to the things which are proposed to him. Accordingly, as regards the first of these, faith must needs be from God.
Because those things which are of faith surpass human reason, hence they do not come to man’s knowledge, unless God reveal them.
To some, indeed, they are revealed by God immediately, as those things which were revealed to the apostles and prophets, while to some they are proposed by God in sending preachers of the faith, according to Rm. 10:15: “How shall they preach, unless they be sent?” ”
St. Thomas Aquinas