Our knowledge comes primarily from experience - what our senses tell us. But is experience really what it seems? The experimental breakthroughs in 17th-century science of Kepler, Galileo and Newton informed the great British empiricist tradition, which accepts a 'common-sense' view of the world - and yet concludes that all we can ever know are 'ideas'. Dave Robinson, with the aid of Bill Mayblin's brilliant illustrations, outlines the arguments of Locke, Berkeley, Hume, J.S. Mill, Bertrand Russell and the last British empiricist, A.J. Ayer.