The following article found at Reformationtheology.com gets to the heart of debates that have gone on for centuries within the Christian community.
Monergism v. Synergism (Quote) by R. C. Sproul
The doctrine of justification by faith alone was debated during the Reformation on the deeper level of monergistic regeneration. This technical term must be explained. Monergism is derived from a combination of a prefix and a root. The prefix mono is used frequently in English to indicate that which is single or alone. The root comes from the verb “to work.” The erg of monergy comes into our language to indicate a unit of work or energy. When we put the prefix and root together, we get monergy or monergism. Monergism is something that operates by itself or works alone as the sole active party. Monergism is the opposite of synergism. Synergism shares a common root with monergism, but it has a different prefix. The prefix syn comes from a Greek word meaning “with.” Synergism is a cooperative venture, a working together of two or more parties.
When the term monergism is linked with the word regeneration, the phrase describes an action by which God the Holy Spirit works on a human being without this person’s assistance or cooperation. This grace of regeneration may be called operative grace. Cooperative grace, on the other hand, is grace that God offers to sinners and that they may accept or reject, depending on the sinner’s disposition.
Monergistic regeneration is exclusively a divine act. Man does not have the creative power God has. To quicken a person who is spiritually dead is something only God can do. A corpse cannot revive itself. It cannot even assist in the effort. It can only respond after receiving new life. Not only can it respond then, it most certainly will respond. In regeneration the soul of man is utterly passive until it has been made alive. It offers no help in reviving itself, though once revived it is empowered to act and respond.
Here we reach the ultimate point of separation between semi-Pelagianism and Augustinianism, between Arminianism and Calvinism, between Rome and the Reformation. Here we discover whether we are utterly dependent on grace for our salvation or if, while still in the flesh, still in bondage to sin, and still dead in sin, we can cooperate with grace in such a way that affects our eternal destiny.
Arminianism reverses the order of salvation. It has faith preceding regeneration. The sinner, who is dead in sin and in bondage to sin, must somehow shed his chains, revive his spiritual vitality, and exercise faith so that he or she may be born again. In a very real sense regeneration is not so much a gift in this schema as it is a reward for responding to the offer of grace. The Arminian argues that in this universal prevenient grace is primary, in that God first offers grace for regeneration. God takes the initiative. He makes the first move and takes the first step. But this step is not decisive. This step may be thwarted by the sinner. If the sinner refuses to cooperate with or assent to this proffered grace, then grace is to no avail.
[excerpts from R. C. Sproul – What is Reformed Theology?]