The doctrine of perseverance may also be proved in an inferential way.
a. From the doctrine of election. Election does not merely mean that some will be favored with certain external privileges and may be saved, if they do their duty, but that they who belong to the number of the elect shall finally be saved and can never fall short of perfect salvation. It is an election unto an end, that is, unto salvation. In working it out God endows believers with such influences of the Holy Spirit as to lead them, not only to accept Christ, but to persevere unto the end and to be saved unto the uttermost.
b. From the doctrine of the covenant of redemption. In the covenant of redemption God gave His people to His Son as the reward for the latter’s obedience and suffering. This reward was fixed from eternity and was not left contingent on any uncertain faithfulness of man. God does not go back on His promise, and therefore it is impossible that they who are reckoned as being in Christ, and as forming a part of His reward, can be separated from Him (Rom. 8:38, 39), and that they who have entered the covenant as a communion of life should fall out.
c. From the efficacy of the merits and intercession of Christ. In His atoning work Christ paid the price to purchase the sinner’s pardon and acceptance. His righteousness constitutes the perfect ground for the justification of the sinner, and it is impossible that one who is justified by the payment of such a perfect and efficacious price should again fall under condemnation. Moreover, Christ makes constant intercession for those who are given Him of the Father, and His intercessory prayer for His people is always efficacious, John 11:42; Heb. 7:25.
d. From the mystical union with Christ. They who are united to Christ by faith become partakers of His Spirit, and thus become one body with Him, pulsating with the life of the Spirit. They share in the life of Christ, and because He lives they live also. It is impossible that they should again be removed from the body, thus frustrating the divine ideal. The union is permanent, since it originates in a permanent and unchangeable cause, the free and eternal love of God.
e. From the work of the Holy Spirit in the heart. Dabney correctly says: “It is a low and unworthy estimate of the wisdom of the Holy Spirit and of His work in the heart, to suppose that He will begin the work now, and presently desert it; that the vital spark of heavenly birth is an ignis fatuus, burning for a short season, and then expiring in utter darkness; that the spiritual life communicated in the new birth, is a sort of spasmodic or galvanic vitality, giving the outward appearance of life in the dead soul, and then dying.” According to Scripture the believer is already in this life in possession of salvation and eternal life, John 3:36; 5:24; 6:54. Can we proceed on the assumption that eternal life will not be everlasting?
f. From the assurance of salvation. It is quite evident from Scripture that believers can in this life attain to the assurance of salvation, Heb. 3:14; 6:11; 10:22; 2 Pet. 1:10. This would seem to be entirely out of the question, if it were possible for believers to fall from grace at any moment. It can be enjoyed only by those who stand in the firm conviction that God will perfect the work which He has begun.
…The denial of the doctrine of perseverance virtually makes the salvation of man dependent on the human will rather than on the grace of God. This consideration will, of course, have no effect on those who share the Pelagian conception of salvation as autosoteric—and their numbers are great—but certainly ought to cause those to pause who glory in being saved by grace. The idea is that, after man is brought to a state of grace by the operation of the Holy Spirit alone, or by the joint operation of the Holy Spirit and the will of man, it rests solely with man to continue in faith or to forsake the faith, just as he sees fit. This renders the cause of man very precarious and makes it impossible for him to attain to the blessed assurance of faith.
—Louis Berkhof, Systematic Theology (Grand Rapids, MI: Wm. B. Eerdmans publishing co., 1938), 547–549.