Definition of Fear: “fear bears on two things, namely, the evil from which someone flees through fear, and whatever seems to be the source of that evil” (215).
Worldly fear: “sometimes it happens that the evil from which someone recoils is contrary to a bodily or temporal good which a person sometimes loves inordinately and recoils from having it injured or destroyed by a mere man. This is human or worldly fear and is not from the Holy Spirit. Indeed, the Lord forbids such fear: do not fear those who kill the body (Matt 10:28).”
Fear of punishment: “There is a second type of fear which recoils from an evil contrary to created nature, namely, the evil of being punished, and shrinks from having this evil inflicted by a spiritual cause, namely, by God. Such fear is praiseworthy in at least one respect, namely, that it fears God. . . But insofar as such fear does not recoil from an evil opposed to one’s spiritual good, namely, sin, but only punishment, it is not praiseworthy. It has this short coming not from the Holy Spirit, but from man’s guilt.” (215-17).
Initial fear: “There is a third type of fear which recoils from evil opposed to a spiritual good, namely, from sin or separation from God, which a person fears to incur from the just vengeance of God. Thus it bears on spiritual goods, but with an eye on punishment. This is called initial fear because it is usually found in men at the beginning of the their conversion. . . . This is the fear mentioned in the Psalm: the fear of the Lord is the beginning of wisdom (Ps 111:10).
Chaste Fear: “The fourth type of fear has its eye entirely on spiritual things, because it fears nothing except separation from God. This is holy fear: the fear of the Lord is holy, enduring forever and ever (Ps 19:10). But just as initial fear is caused by imperfect love, so this fear is caused by perfect love: perfect love casts out fear (1 John 4:18).
Romans 8:14-17, Commentary on the Letter of Saint Paul to the Romans (Lander: The Aquinas Institute for the Study of Sacred Doctrine, 2012).