These "decisive moments, " as Cartier-Bresson was wont to call them, summon up imagined chatter and repartee, so unlike the still, stubborn muteness inherent in Strand's work.

WSJ: Review: Two Sides of the Same Coin | 'Henri Cartier-Bresson/Paul Strand, Mexico 1932-1934' at Fondation Cartier in Paris

With an iPhone or Android app, you call up the Uber map, spot an available town car or taxi, and summon it with a click.

WSJ: The Weekend Interview with Travis Kalanick: The Transportation Trustbuster