We have a problem. We thought that the internet would open our minds, but instead we've created a machine that is closing them. Our online world is increasingly accessed through social media. For many it's now their primary news source – served algorithmically, only with the opinions and values we want to see. This is driving divides in society pushing opinions to their extremes: from the posturing of Trump, to Brexit, to Gamergate. It's time social media platforms took responsibility for their influence. Should we trust private companies with the shaping of society? How can we adjust feed algorithms for maximum impact? Is there ever a "good" way to manipulate sentiment?