A Helpful Follow Up on Regeneration
When people ask me what is the heart of the doctrines of grace, I usually respond by saying one central essential thing: "salvation is of the Lord" (cp, Psalm 37:39; Jonah 2:9). That is the glory of our new life in Christ... it is all of Him; He saved us and not we ourselves. (Titus 3:5). It is all of grace (Eph. 2:8-9) for apart from we can't do anything (John 15:5); and before we are saved by His grace through faith in Christ alone, we were dead in trespasses and sin, by nature children of wrath, sons of disobedience, slaves to our own lusts, passions and desires (Eph. 2:1-3; Titus 3:3, Rom. 3:10-18).

John Hendryx has done an amazing, concise work on the two views of regeneration. I hope this will encourage you in the greatness of our Lord's saving work for His elect and that it would cause you to glory afresh in the finished work of the Lord Jesus Christ alone.

Defining the Terms
Monergism: The doctrine that the Holy Spirit is the only efficient agent in regeneration - that the human will possesses no inclination to holiness until regenerated, and therefore cannot cooperate in regeneration. Monergism is when God conveys that power into the fallen soul whereby the person who is to be saved is enabled to receive the offer of redemption. It refers to the first step (regeneration) which has causal priority over, and gives rise to, the spiritual ability to comply with all the other aspects of the process of being united to Christ, (i.e., the ability to apprehend the Redeemer by a living faith, to repent of sin and to love God and the Mediator supremely) It does not refer to the whole process that it gives rise to (justification, sanctification), but only the granting of the spiritual capacity to comply with the terms of the covenant of grace.

Synergism: "...the doctrine that there are two efficient agents in regeneration, namely the human will and the divine Spirit, which, in the strict sense of the term, cooperate. This theory accordingly holds that the soul has not lost in the fall all inclination toward holiness, nor all power to seek for it under the influence of ordinary motives." This unscriptural view is the greatest threat to a true understanding of salvation in the Church today.

The following comparison highlights some of the major points of difference in these systems:

Two Views of the Cause of Regeneration
Synergism
Faith is the cause that triggers regeneration

Faith and affections for God are produced by the old nature.

God and Man work together to produce the new birth. God's grace takes us part of the way to salvation, man's unregenerate will must determine the final outcome.

God is eagerly awaiting the sinner's will.

The persons of the Trinity have conflicting goals in accomplishing and applying salvation: The Father elects a particular people; The Son dies for a general people and the Holy Spirit applies the atonement conditionally on those who exercise their autonomous free will.

Restoration of spiritual faculties comes after the sinner exercises faith with his natural (innate) capacities. Has the ability to see spiritual truth even before healed. (see 1 Cor 2:14). Has spiritual capacity to receive the truth, prior God's granting any spiritual ability.

Monergism
Regeneration is the cause of faith. (has causal priority)

Faith is not produced by our unregenerated human nature. It is the immediate and inevitable product of the new nature.

God, the Holy Spirit, alone produces regeneration with no contribution from the sinner. (A work of God)

God effectually enables the sinner's will.

The persons of the Trinity work in harmony - The Father elects a particular people, Christ dies for those the Father has given Him and the Holy Spirit likewise applies the benefits of the atonement to the same.

"Light" itself is not enough for a blind man to see, his vision must first be restored. (John 3:3,6). Needs spiritual ability to receive truth prior to receiving it.

Two Views of Humanity
Synergism
The fallen sinner has the ability and potential inclination to believe even prior to the new birth

The Gospel is an invitation

Christ died for all our sins except unbelief

There is enough good left in fallen man to turn his affections toward Christ.

Sinner needs help, is spiritually handicapped.

Natural man is sick and disabled like a drowning man so God would be unfeeling if He didn't help by casting a rope.

Needs salvation from the consequences of sin - unhappiness, hell, psychological pain

The natural man is sovereign over his choice to accept or reject Christ - God conditionally responds to our decision.

Some fallen men either created a right thought, generated a right affection, or originated a right volition that led to their salvation while some other fallen men did not have the natural wherewithal to come up with the faith that God required of them to obtain salvation. Therefore salvation is dependent on some virtue or capacity God sees in certain men.

Man's nature & affections do not determine or give rise to his choices. He can still make a saving decision prior to the new birth while still in his unregenerate state. In this scheme God gives enough grace to place man in a neutral position which can swing either for or against Jesus. (An act of chance?)

Monergism
The fallen sinner has no ability or inclination to believe prior to the new birth.

The Gospel is not merely an invitation but a command (1 John 3:23)

Christ died for all our sins including unbelief

Fallen Man has a mind at enmity with God; loves darkness, hates the light and does not have the Holy Spirit. "There is no one who seeks God" (Rom 3:11); Sinner would never turn to God without divine enablement and new affections.

Spiritually dead sinner needs new nature (mind, heart, will), regeneration.

Natural man is spiritually impotent and morally culpable for both original sin and actual sins committed. Our inability is not like a physical handicap or a drowning man for which we would not be culpable but, rather, it is like a man who cannot repay a squandered financial debt. Inability to repay, therefore, does not relieve us of the moral responsibility to do so.

Needs salvation to remove the offense we've made against a holy God and from the power and bondage of sin.

The natural man can contribute nothing towards his salvation. Faith is a response rendered certain following the efficacious work of the Holy Spirit.

We respond to God's unconditional decision. (Acts 13:48)

No Fallen man will create a right thought, generate a right affection, or originate a right volition that will lead to his salvation. We would never believe unless the Holy Spirit came in and disarmed our hostility to God. Therefore salvation is dependent on God's good pleasure alone (Eph 1:4, 5, 11), not something He sees in us.

Man's nature determines his desires/affections and give rise to the choices he makes. "No good tree bears bad fruit, nor does a bad tree bear good fruit." Luke 6:43 Only Christ can "make a tree good and its fruit will be good."
(Also see John 8:34, 42-44; 2 Pet. 2:19).

Two Views of the Gospel
Synergism
Sinners have the key in their hands. Man's will determines whether or not Christ's death is efficacious.

It would be unjust of God to not give everyone an equal chance.

After God makes one's heart of stone into a heart of flesh the Holy Spirit's call to salvation can still be resisted.

Salvation is given to fallen sinners (unregenerate) who choose and desire Christ of their free will.

The grace of God is conferred as a result of human prayer

God has mercy upon us when we believe, will, desire, strive, labor, pray, watch, study, seek, ask, or knock, apart from his regenerative grace.

Commands to repent and believe the gospel imply the ability of the sinner to do so.

God helps those who help themselves.

Unregenerate man contributes his little bit.

Repentance is considered a work of man.

One of the greatest gifts God gives humans is to never interfere with their free will.

With Man's will salvation is possible.

Monergism
God has the key in his hand. God's eternal counsel determines to whom the benefits of the atonement apply.

If God exercised His justice then none of us would stand since each of us has rebelled against an infinitely holy God. He owes us nothing and is under no obligation to save any person. Regeneration is, therefore, an act of pure, undeserved mercy because the justice we deserved, He poured out on His Son (thereby turning His wrath away from us).

After God makes one's heart of stone into a heart of flesh, no person wants to resist. By definition our desires, inclinations and affections have changed so we willingly and joyfully turn in faith toward Christ.

Apart from grace, there is no fallen sinner (unregenerate) who fits that description. A desire for God is not part of the old nature.

It is grace itself which makes us pray to God (Rom 10:20; Isa. 65:1)

To desire and seek God prior to the new birth is an impossible supposition. (Rom. 3:11; 1 Cor 2:14) It is the infusion and quickening of the Holy Spirit within us that we even have the faith or the strength to will, desire, strive, labor, pray, watch, study, seek, ask, or knock and believe in the finished work of Christ.

The Command toward sinners to repent and believe does not imply ability. Divine intent is to reveal our moral impotence apart from grace (Rom 3:20, 5:20, Gal 3:19,24). The Law was not designed to confer any power but to strip us of our own.

God only helps those who cannot help themselves. (John 9:41)

Nothing in my hands I bring, simply to Thy Cross I cling.

Repentance is a gift of God. (2 Tim 2:25)

The greatest judgment which God can inflict upon a man is to leave him in the hands of his own free-will. If salvation were left in the hands of the unregenerate sinners, we would indeed despair of all hope that anyone would be saved. It is an act of mercy, therefore, that God awakens the dead in sin to life since those without the Spirit cannot understand the things of God at all. (1 Cor 2:14)

With man's will salvation is impossible but with God all things are possible. (Matt 19:26; Rom 9:16; John 6:64,65) "Flesh gives birth to flesh, but the Spirit gives birth to spirit." (John 3:6)

Note: God acts unilaterally, taking the sole initiative in a free act of sovereign grace toward the sinner—grace that is altogether prior to, and effectually produces, justifying faith. The response of faith from the sinner is penultimate as it stands next to the ultimate sovereign grace of God in Monergism. As the first act of a newborn baby is to breathe, so the act of faith is the first act of the regenerated sinner, in his/her new birth in Christ.