Definite atonement, or limited atonement, is the Reformed conviction that Christ's death was specifically designed by the Father and effectively accomplished by the Son to secure the salvation of the elect. While some Christian traditions hold that Christ died for every individual in the same way, the Reformed tradition emphasizes that the purpose and result of Christ's sacrifice are inseparably linked, ensuring that all for whom He died are infallibly saved.
The doctrine of definite atonement is rooted in the inseparable connection between the divine counsel and the actual effect of Christ's death. As stated in the 1689 LBCF Ch.8 §5, Christ by His obedience and death fully discharged the debt of all those who are justified. Our Lord himself confirms this when He says in John 10:15, "even as the Father knoweth me, and I know the Father; and I lay down my life for the sheep." This teaches us that the scope of the atonement is defined by the Father's gift of a specific people to the Son. To suggest that Christ died for all men in the same way while many are not saved is to suggest that His death can fail to achieve its intended goal, which would undermine the perfect satisfaction of Christ.
This doctrine is not intended to limit the value of Christ's sacrifice, which is of infinite worth, but to affirm the certainty of its application. Because Christ is our surety, as noted in the 1689 LBCF Ch.8 §8, His work effectively reconciles the elect to God. We can confidently say with the Apostle Paul, "Who shall lay anything to the charge of God's elect? It is God that justifieth; who is he that condemneth? It is Christ Jesus that died, yea rather, that was raised from the dead, who is at the right hand of God, who also maketh intercession for us" (Romans 8:33-34). We preach this gospel to all because we do not know the elect, and it is the power of God unto salvation for everyone who believes.