Given the exponential increase in human knowledge in the twentieth and twenty-first centuries, there is often an unspoken assumption that we have explained a phenomenon if we have labeled it or are able to account for its cause in the natural world. While it is doubtless true that labeling phenomena and figuring out the natural causes of such things as diseases can represent a growth in understanding, our confidence in our knowledge is often misplaced. We still face many limitations in our ability to figure out the world. For instance, although we have given the label gravity to the force that keeps us grounded on earth so that we do not go flying off into space, we still do not know exactly what gravity is. We know what gravity does, but we do not really know its ontology, its "beingness."
In theology, we face a similar difficulty when it comes to the doctrine of providence. We know that the Lord governs all things, but we do not understand fully how God works in and through His creation to accomplish His purposes. Nevertheless, theologians often employ the useful term concurrence to explain the reality that God and human beings both act at the same time so that the Lord's plan is fulfilled and our choices are really and truly our own.
In essence, concurrence says that two or more parties can act in the same event and produce a given outcome without all parties having the same intent. Job's life is a good illustration of concurrence. In Job 1, we read of three major players in Job's suffering. Satan instigated the suffering by issuing a challenge to the Lord regarding Job's piety. God allowed Satan to bring suffering into Job's life. The Chaldeans and the Sabeans attacked Job's family and stole his livestock. But the intent of each party in producing the same outcome—Job's suffering—was different. Satan intended to discredit Job, and by extension, to discredit God. The intent of the Chaldeans and Sabeans was to enrich themselves. Our Lord's intent was to vindicate Job's faith. Each of these players was necessarily involved in Job's suffering, but at different levels and with different motivations. There was a concurrence among them that Job should suffer, but each had a different reason for this suffering. God's intent was good. The other players intended evil.
Concurrence helps explain how God can ordain evil and not be guilty of sin. He has a holy intent in all He ordains. Evil is evil, but the Lord never has an evil intent, and He never does evil Himself. He works through the evil intents of others to fulfill His good intent.
One of the best examples of concurrence in Scripture is seen in the death of Christ. God ordained the crucifixion and evil men acted to bring it about. Both were necessary for Christ's death to take place. But God had the good intent to save His people and exalt His Son for His sacrificial obedience, while the men who killed Christ had the evil intent simply to do away with Him. God is sovereign over evil, which gives every evil an ultimate purpose, but He remains entirely good.