From their dealings at Marburg, Zwingli wrote his friend Vadian the following about Melanchthon:
Melanchthon I found uncommonly slippery; he kept changing his shape like another Proteus, forced me—in lieu of salt!—to use my pen as a weapon and keep my hand dry, so that I could hold him fast for all his chafings and wrigglings and dodgings. I am sending you a copy of a few extracts from our very lengthy conversations on the understanding that you will only show it to those you can trust—I mean, to those who will not use it to stir up another crisis: remember that Philip [Melanchthon] has a copy too, for I drew it up in his presence and under his eye, and many of his own words he actually dictated. But the last thing we want is to bring on a new crisis. Philip and I spent six hours together, Luther and Oecolampadius three.
Slippery… that actually sums Melanchthon up quite well.