Father Geiermann mentions five properties of actual grace: necessity, gratuity, efficacy, universality, and inequality. He says that actual grace is necessary for four reasons:
First, “Man needs the light of grace to find the truth. Though he can learn many things in the natural order by persevering application, he needs the help of God to master all human science. ‘For the corruptible body is a load upon the soul, and the earthly habitation presseth down the mind that museth upon many things’ (Wis 9:15). In the supernatural order actual grace must enlighten man’s mind and prompt his will before he can accept the truths of divine revelation. ‘No man can come to Me,’ says the Saviour, ‘except the Father, who hath sent Me, draw him’ (Jn 6:44).”
Secondly, “Man needs actual grace to do good. It is true that in the natural order man can of himself do some good, but he can not keep the entire natural law without the grace of God. Much less can he of himself do good supernaturally, that is in a way meritorious for heaven. For the Saviour says: ‘Without Me you can do nothing’ (Jn 15:5).”
Thirdly, “Man needs the grace to overcome temptation. By his unaided strength man can overcome the lesser, but not the graver temptations of life. . . . Hence, man needs the help of actual grace to avoid mortal sin, and though he can avoid some venial faults of himself, he requires the most special help of God to avoid all deliberate venial sin.”
Fourthly, “Man needs the grace of God to persevere in doing good. Perseverance may be considered as temporal and as final. In either case grace is necessary to persevere.”
“Final perseverance, or perseverance in the grace of God till death, is a special favor which can be obtained only by persevering prayer. Three things unite to produce final perseverance: sanctifying grace, the special dispensations of Divine Providence, and a chain of actual graces. Man obtains the first through Baptism, sacramental absolution, perfect contrition and perfect love of God. He secures the second by embracing the state in life to which God has called him, by fulfilling the duties of his state in life, by submitting to the guidance of Providence, and by obeying the inspirations of grace.” As for the chain of actual graces, Father Geiermann notes that “though man can never merit a single grace, much less the chain of graces necessary to persevere in God’s friendship until death, he can obtain this priceless grace by fidelity and persevering prayer.”
Quotations from Peter Geiermann, The Narrow Way (New York: Benziger, 1914).