A Centre for Mitochondrial Research was established this year at Newcastle University. But its proposed techniques cannot be tested in clinical trials without a change in the law, so the government has commissioned a ‘public dialogue’. Such procedures address the feelings prompted by scientific advances, but often also result in substantive moral objections being condescendingly dismissed as the irrational ‘yuck’ reaction. There seems to be scant room for moral or political rather than scientific arguments. What roles should democracy, morality and a grasp of the actual science play in the process of making decisions on such issues? The speakers in this Battle of Ideas science session reveal all.