THE CUP ARGUMENT FOR PSA DOESN'T HOLD WATER

I have written elsewhere that I have never seen convincing Scriptural proof for the Penal Substitutionary Atonement theory's assertion that on the cross God poured out his righteous wrath on His Son so that God might remain just (by punishing sin appropriately) but also loving (by offering us forgiveness). 

A respected friend from across the aisle recently wrote, however, that he finds scriptural support for PSA in Jesus' reference to His impending death as a "cup" from God's hand in light of what a "cup" symbolized in the Old Testament. 

Many passages, the argument goes, use the cup as a metaphor for God's wrath. 

For example Psalm 75:8 -

In the hand of the Lord is a cup
full of foaming wine mixed with spices;
he pours it out, and all the wicked of the earth
drink it down to its very dregs.

On the surface, this looks like a convincing argument: The Lord does often hand out a steaming cup of wrath in the Old Testament. 

But there are problems.

1) Even if the majority of the Old Testament references to cups are negative, not ALL are. Most famously, King David wrote "my cup runneth over". Was it overflowing with God's wrath? Psalm 116 references the "cup of salvation". 

This illustrates a wider problem, then.

2) A cup is simply a vessel. It can hold something terrible, like wrath, or it can hold something refreshing, like blessings. The cup holds whatever God is handing to you. 

IF Jesus had said, "Father, if possible, take this cup OF YOUR WRATH from me", I would feel differently about this argument for PSA. But he never says what the cup is full of. Could it not be simply a cup of suffering?

But having said all that, one need look no further than the Gospel of Mark to see the cup argument for PSA fall apart completely. 

Remarkably, I saw a proponent of PSA writing for Ligonier Ministries cite Mark 10 as evidence of the cup Jesus drank being God's wrath. He quoted verses 35 to 38:

35 And James and John, the sons of Zebedee, came up to him and said to him, “Teacher, we want you to do for us whatever we ask of you.” 36 And he said to them, “What do you want me to do for you?” 37 And they said to him, “Grant us to sit, one at your right hand and one at your left, in your glory.” 38 Jesus said to them, “You do not know what you are asking. Are you able to drink the cup that I drink, or to be baptized with the baptism with which I am baptized?” 

Obviously, the implied answer to Jesus' question is "No" - it is His alone to drink the "cup of God's wrath". The author concludes that "cup" here necessarily "represents the cup of divine wrath that Jesus would drink on behalf of His people to save them from their sin." But notice the words "of divine wrath" do not appear in this passage. 

To his credit, the writer does acknowledge that the conversation did not end there. He mentions, but does not quote, verses 39 to 40:

39 And they said to him, “We are able.” And Jesus said to them, “The cup that I drink you will drink, and with the baptism with which I am baptized, you will be baptized, 40 but to sit at my right hand or at my left is not mine to grant, but it is for those for whom it has been prepared.”

Somehow, in the writer's mind, we are no longer talking about the cup of God's wrath. Instead, "Jesus was pointing to the fact that in a sense, they would share in the ordeal Christ was about to undergo in Jerusalem", i.e. they would suffer.

I agree with his conclusion - Jesus is saying the disciples will have a similar cup from God's hand, a cup of suffering. 

I am just not sure why Jesus' cup is assumed to be God's wrath in verse 38. If that is the proper reading of the first part of the passage, don't we have to be consistent and maintain that Jesus told His disciples in the second half that they would also drink the cup of God's wrath?