A 1688 riddle about sight and touch got tested on real patients three centuries later

William Molyneux asked Locke whether a blind person, upon suddenly gaining sight, could visually identify a cube and sphere they'd only ever known by touch. In the 2000s, Pawan Sinha's Project Prakash gave blind children in India sight-restoring surgery and tested exactly this. The newly sighted couldn't match shapes by eye within 48 hours, but learned to within days, finally answering Molyneux with a qualified no.

— Richard Held et al., The newly sighted fail to match seen with felt — Nature Neuroscience, 2011