Thomas Aquinas

“ Now the principle of all appetitive movements is the good or evil apprehended: and consequently the principle of fear and of every appetitive movement must be an apprehension. Again, through faith there arises in us an apprehension of certain penal evils, which are inflicted in accordance with the Divine judgment. In this way, then, faith is a cause of the fear whereby one dreads to be punished by God ”

“ It is also the cause of filial fear, whereby one dreads to be separated from God, or whereby one shrinks from equalling oneself to Him, and holds Him in reverence, inasmuch as faith makes us appreciate God as an unfathomable and supreme good, separation from which is the greatest evil, and to which it is wicked to wish to be equalled. Of the first fear, viz. servile fear, lifeless faith is the cause, while living faith is the cause of the second, viz. filial fear, because it makes man adhere to God and to be subject to Him by charity. ”

“ Things that are in the intellect are the principles of those which are in the appetite, in so far as the apprehended good moves the appetite.
Reply to Objection 2: Even lifeless faith excludes a certain impurity which is contrary to it, viz. that of error, and which consists in the human intellect, adhering inordinately to things below itself, through wishing to measure Divine things by the rule of sensible objects. ”