The Difference Between Christ and Mary

Thomas Aquinas doesn't typically talk about Christ as a meritorious cause of Grace is given before his incarnation. But that's specifically in the definition that this is by virtue of the merits of Christ, so that something that Jesus hasn't done yet is already meriting for Mary this grace. That tells us something about the plan of God, that Mary is being included in the plan of the incarnation from the very beginning here and she's receiving the fruit of that already.