Barack Obama cut short his post-presidential vacation today (April 24) to speak to students at the University of Chicago, in his first public appearance since leaving the White House in January. What was most striking about Obama’s discussion today was the one word he didn’t mention: Trump. Nowhere in Obama’s more-than-hour speech did the former president touch upon his thoughts on US president Donald Trump’s public comments or policy decisions. Though aides have mentioned before (paywall) that Obama doesn’t want to use his platform to challenge the new president, this is the first time we’re seeing that refusal play out. Anyone anxiously hoping for Obama to stand as an opposing force to the new administration will just have to keep holding their breath. Addressing a crowd of about 400, the former president—who held a forum-style chat on stage with a panel of high school and college students—spoke about his interest in encouraging leadership, pressed the importance of civic engagement in a fractured political climate such as today’s, and dispensed career advice. “Worry less about what you want to be, and worry more about what you want to do,” the former president told students, when asked what kinds of guidance he typically gives White House interns and other young people. The majority of Obama’s speech centered around the problem of social-media filtering—a concern he also discussed in his presidential farewell address in January. At that time, Obama warned of a “great sorting” caused by splintering media channels and political bubbles on platforms such as Facebook. Under Trump’s administration, the public’s partisanship and apathy have become even bigger concerns for politicians all over. The former president today encouraged students in his audience today to take action against both matters, noting: These days, you don’t have to confront people if you have different opinions. If you’re liberal, you’re on MSNBC. If you’re conservative, you’re on Fox News. You’re either reading the Wall Street Journal or the New York Times. Or you’re watching cat videos, which is fine.