A.T. Robertson Commentary Romans 11:24

"For if thou wast cut out of that which is by nature a wild olive tree, and wast grafted contrary to nature into a good olive tree; how much more shall these, which are the natural [branches], be grafted into their own olive tree?" — Romans 11:24 (ASV)

Contrary to nature (παρα φυσιν). This is the gist of the argument, the power of God to do what is contrary to natural processes. He put the wild olive (Gentile) into the good olive tree (the spiritual Israel) and made the wild olive (contrary to nature) become the good olive (καλλιελαιος, the garden olive, καλλος and ελαια in Aristotle and a papyrus).

Into their own olive tree (τη ιδια ελαια). Dative case. Another argument a fortiori, "how much more" (πολλω μαλλον). God can graft the natural Israel back upon the spiritual Israel, if they become willing.