Barbara Stanwyck is freakin amazing in this movie too. She is rail thin, rangey, she talks a mile a minute, a ball of nervous energy. Every scene she's in seems to run about twice as fast. Gary Cooper is better here than in "Mr Deeds Comes To Town" -- he plays a guy who maybe isn't the sharpest tool in the shed; his struggle to understand what's happening to him plays on his face like it's a movie screen. His timing here is better, and he and Stanwyck have real chemistry.
Capra didn't just make great entertainments, he didn't just develop his own grammar of modern cinema. He managed to find a way to fuse realism with a conscious artifice in a way that's irresistable.
By which I guess I mean this: A Capra movie is a well oiled narrative machine; nothing is there without a reason, every element is there to move the plot forward; every pause a punctuation, every sentence as rhythmic and cadenced as Shakespeare. At the same time, it's possible to completely lose yourself
in his movies -- for 90 minutes you're living in his world. His characters, while being heroic in large and small ways are still people in the round -- with doubts, fears, appetites, and anger.
And as near as I can tell, all his movies have a common message, that love redeems people's moral comprimises and mistakes. Love is the goad that makes them be the better person they wished they were in the first place. Love pulls people back from the brink. Combine that with a sentimental populism
and there isn't a dry eye in the house.
Oh, and Barbara Stanwyck was in the crucial noir thriller "Double Indemnity" with Fred McMurray. Both actors were trivialized artistically by their late-career work, but they blaze in this one. They generate more heat with their clothes on than a thousand nude scenes.