Earlier today Pope Francis gave the first ever Papal address before congress. The word "historic" has even thrown about.
The photo above was captured in the instant prior to the handshake between Pope Francis and Joe Biden. Note that the Vice President holds his hand perpendicular to the floor (which, in most all other scenarios would be highly recommended - but not in front of the World - with the Pope - particularly if you're Catholic [as are both Joe Biden and John Boehner]). Such a hand orientation suggests parody. Yet with a high-level religious figure such as Pope Francis (regardless of one's spiritual practice), Mr. Biden would be well advised to adopt a handshake with deference.
In the image below (at the very end of the same handshake), Mr. Biden realizes his mistake and although not optimally configured, he attempts to salvage the situation and partially retracts his fingers - and more fully repositions his thumb. Despite Biden being significantly elevated, this allows Francis' thumb to be on top and thus shifts the Pope to a relative alpha status.
In contrast, John Boehner, either via instinct or from witnessing the Vice President's mistake, offers his hand in a palm-up manner from the beginning. Normally neither Biden nor Boehner would want to accept a beta role in the context of a handshake - or otherwise.
Of course, many other people in power positions have egos which crave the lowering other high-power alphas to relative beta positions. Yet Pope Francis is an exception to this very human foible (He doesn't "need" or want others to behave this way). And Boehner and Biden are wise to make this exception versus their typical salutations.
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