J I Packer writes a great chapter on the necessity of the atonement in the little collection, suitably entitled, Atonement, edited by Gabriel N. E. Fluhrer (P & R, 2010). To make his case he looks at Romans 8:32, which says:
He who did not spare his own Son but gave him up for us all, how will he not also with him graciously give us all things? (ESV)
Packer goes on to argue:
If [God] could have spared his own Son and still redeemed, we may be sure he would have. God doesn’t make needless gestures. The Father’s sacrifice of the Son tells us, as sure as eggs are eggs … , that it had to be done this way. Our redemption couldn’t be achieved at any lesser cost. If the gesture had been needless, it wouldn’t have been a wonderful display of love. The glory of Calvary as the demonstration of God’s love would be like a punctured balloon. If it were not necessary, then there is nothing wonderful about it after all.
It is a great argument. It makes me wonder: if we (I) struggle to appreciate God’s love in the giving of his Son, is it because we (I) secretly believe he could have done it some other way?