People can certainly issue naked offers and threats. But the clarity of “You scratch my back, I’ll scratch yours” or “Your money or your life” comes with costs. The exchange may be taboo, as in prostitution, bribery or extortion, and even when it is legitimate, overt deal-making can be disagreeable. Each side must hold the other to the terms of a hard bargain, sacrificing flexibility and making the relationship feel cold and transactional.

For these reasons people often cloak their exchanges in the trappings of a communal relationship, in which friends, relatives or comrades share goods unstintingly, with no one keeping track. Deals that are struck under the charade of a fictive friendship may have more forgiving terms, and the parties may throw in sweeteners to secure the other’s loyalty and cement the relationship.

Thus, businesspeople may treat their customers as faux friends. Conversely, casual companions (who often do have to exchange favors) take pains to avoid any impression that they are dickering for goodies or bossing each other around. They soften each other up with sympathetic banter and pleasantries. And they couch any request as an idle observation, such as “I was wondering if you could pass the salt,” knowing that the hearer will mentally fill in the premise that turns the non sequitur into a sequitur.

Often the genteel hint consists of a prerequisite to the favor. It makes no sense to ask someone to pass the salt if you already have the salt, if you don’t like salt or if the hearer is incapable of passing the salt. So by airing a thought like “There isn’t any salt down here,” “I could use some salt” or “Can you pass the salt?” a polite diner can plant the desired next step into the head of his tablemate and get what he wants without seeming to treat her like a flunky.

The Trump-Zelensky dialogue could be used in the chapter of a linguistic textbook on conversational analysis. The exchange begins with the two leaders cementing a communal relationship with fulsome congratulations and flattery and a celebration of their similarities and common interests. Mr. Trump abruptly steers the conversation to the prerequisites of calling in a favor. He reminds his interlocutor (three times) that the United States has been good to Ukraine, that the United States now is in need (“Things are happening that are not good”) and, with some token hedging, that America’s goodness remains to be repaid (“I wouldn’t say that it’s reciprocal necessarily”).