If you are going to read this post, don’t read it just once. It would be better to not read it than to read it once. As you read it, remember, he is describing the four parties involved in your salvation.
“First, the originating cause of salvation is the eternal purpose of God, or in other words, the predestinating grace of the Father. Second, the meritorious cause of salvation is the mediation of Christ, this having particular respect to the legal side of things, or, in other words, His fully meeting the demands of the Law on the behalf of and in the stead of those He redeems. Third, the efficient cause of salvation is the regenerating and sanctifying operations of the Holy Spirit, which respect the experimental side of it; or, in other words, the Spirit works in us what Christ purchased for us. Thus, we owe our personal salvation equally to each Person in the Trinity, and not to one (the Son) more than to the others. Fourth, the instrumental cause is our faith, obedience, and perseverance: though we are not saved because of them, equally true is it that we cannot be saved (according to God’s appointment) without them.”
– Quote from A Fourfold Salvation by A.W. Pink