In the 1920s, George L. Stout, now more famously known as the inspiration for the George Clooney character in The Monuments Men, was a conservator with Harvard’s Fogg Museum of Art. With an inter-disciplinary group of scientists, art historians, and fellow conservators, he developed the three-legged stool approach to art authentication.
Scientifically based, the three legs are:
When the system was created, connoisseurship alone was the standard. Stout wrote that questioning a connoisseur’s opinion, “was as naughty as inquiring about the digestive system of an opera singer…it wasn’t proper. And that was very good for the trade.” Logic and science gradually caused a change in both thinking and practice. The three-legged stool concept is now the accepted norm ethically and judicially.
All Rights Reserved
 National Academies Press, Scientific Examination of Art: Modern Techniques in Conservation and Analysis (National Academies Press, 2005), 42-43
 Ibid, 43.