Which half? One day when I was a junior medical student, a very important Boston surgeon visited the school and delivered a great treatise on a large number of patients who had undergone successful operations for vascular reconstruction. At the end of the lecture, a young student at the back of the room timidly asked, "Do you have any controls?" Well the great surgeon drew himself up to his full height, hit the desk, and said, "Do you mean did I not operate on half of the patients?" The hall grew very quiet then. The voice at the back of the room hesitantly replied, "Yes, that's what I had in mind." Then the visitor's fist really came down as he thundered, "Of course not. That would have doomed half of them to their death!" God, it was quiet then, and one could scarcely hear the small voice ask, "Which half?" E.E. Peacock Jr., Seeing With Fresh Eyes science
The innocence of the eye The perception of solid form is entirely a matter of experience. We see nothing but flat colors; and it is only by a series of experiments that we find out that a stain of black or grey indicates the dark side of a solid substance... The whole technical power of painting depends on our recovery of what may be called the innocence of the eye; that is to say, of a sort of childish perception of these flat stains of color, merely as such, without consciousness of what they signify, as a blind man would see them if suddenly gifted with sight. John Ruskin, The Elements of Drawing The skill of perceptionthe innocent i iseeingperception