“If a tree falls in a forest and no one is around to hear it, does it make a sound?” That question grew from a thought experiment conducted by George Berkeley in 1710. Berkeley argued that if no one was around to perceive the trees, then the trees didn’t exist. Citizen journalism seems to affirm Berkeley’s conclusion that perception plays a key role in determining what’s real. Starting with the Rodney King incident, ordinary people armed with cameras have made society aware of all sorts of happenings that previously  were known only by those immediately involved. Which brings us to citizen journalist Melissa DePino, who recently was in a Starbucks in Rittenhouse Square (Philadelphia). Ms. Depino saw police arrest two black men, who had done nothing illegal. But DePino didn’t just “see” the event. She, along with a few others, recorded the event and shared it on Twitter, where it went viral.

Ms. Depino’s video speaks for itself. It’s impact was quick and significant. But also important is what this citizen journalist said  about the making and sharing her video. The behind-the-scenes story—in the CNN interview (above) and in a WHYY interview —highlights the growing role that participatory journalism plays in society. Building on Berkeley’s 400-year-old sight, the implicit message is that the news exists only if we capture it.