How exactly does one decide to bring a child into this world – with the oceans, and the climate, and the, you know, everything else? Surely the kid’s Eiffel Tower-sized carbon footprint is reason enough not to. But what if baby grows up to solve the world’s problems? Then again, what if baby grows up to be a mass murderer? Or what if…? And what if…? If…? What begins as an odd question for a couple in line at Ikea soon becomes much more as they grapple with existence itself as a moral question, in Duncan Macmillan’s timely and startlingly funny Lungs.