The All But Obligatory Signature

"The importance attached to the notion of the individual from the 14th century onwards and the idea that masterpieces are the product of the unique imagination of individuals of genius contributed to popularizing the practice of signing work and indeed made it all but obligatory."

"...painters rarely stick to one signature throughout their career. Often the particular form taken by a signature will indicate that a work was produced during certain years"

-- Nadeije Laneyrie-Dagen, How to Read Paintings, p2.