 Condillac was aware that these claims had been challenged by such empirical studies of recovered vision as were available at the time. In 1728, the English surgeon, William Chesselden, had reported to the British Royal Society that subjects recovering from operations to remove cataracts that had blinded them since birth appeared to need to learn to associate what they saw with tactile experience before they could recognize shapes or objects. Condillac replied to this contrary evidence by claiming that it would take some time for newly sighted subjects to learn how to focus the eyes in order to perceive colours distinctly, and so to see their outlines. It would then take time for the subjects to attend to the shapes that distinctly seen colours exhibit, since we can expect that at first they would be overwhelmed and confused by the variety of information presented by the eyes, much like a person gaining a first glimpse of a Bosch painting. Finally, even after they came to see colours as, say, outlining square or round shapes, they might still hesitate to assume that simply because an object looks to have a certain shape, that therefore it must be felt to have that shape as well. For all of these reasons, time might pass and the subject might appear to be learning to associate visual experiences with tangible objects, even though the colours that are originally seen are already extended and shaped in three dimensions (Essay I.vi. §16).