Some posters on Strictly Platonic want to buy things for other people; some posters want things bought for them. One woman is eager to listen to any guy, any guy at all, natter on about Park Slope in Brooklyn — “You can show me where you like to shop, tell me some history about the area or chitchat about whatever you want” — if he will treat her to a single glass of wine. Another one is willing to pick up the tab for everything and even prove that his wife knows he is on Craigslist looking for female friends, if a woman will just go see some plays with him.

A Strictly Platonic poster generally has something in the world he desires to see or enjoy — something grand, like nature, philosophy, “all the city has to offer” — and he has discovered he needs another person to help him do it. But he doesn’t want to fall in love with that person, or not just yet; so he asks for someone to go biking with — or swimming. Or bar-hopping.

The forum is enlightening because it represents a collaborative effort to define “platonic” — and define it against nearly everything else on Craigslist. You would think the word would be debased by now. But it’s surprisingly intact. Maybe that’s why we still need some notion of platonism in everyday life. Once we’ve stipulated that commercial culture is that which debases everything, we need a popular concept that helps us resist debasement.

Points of Entry: This Week's Recommendations

IT'S ALL GREEK For the Hellenist who has everything, consider "Apanta ta tou Platonos. Omnia Platonis Opera," from Krown & Spellman Booksellers, available on Abebooks for $65,000. It's a 1513 Venetian edition in Greek, with a Welsh inscription.

WHAT DEBT CRISIS? Lots of localized Strictly Platonic listings contribute to the pop definition of "platonic." When it comes to Plato's homeland, however, you'll find "Party people looking for more party people!!" On Craigslist Greece.

SOUL WINDOWS Strictly Platonic is to philosophical loners as Craigslist's Missed Connections is to romantic hipsters. The New York City version of the section, where posters register fleeting glances, is heavy on eye-contact encounters on the L train to and from Brooklyn.