Picasso: Masterpieces of the Blue Period

Why do I date everything I do. Because knowing the works of an artist alone is not sufficient. It is also necessary to know he created them, why, how, under what circumstances. Someday there will doubtless be a science which perhaps will be called "the science of man" and which will strive towards a deeper understanding of a man through the creative person. I often think of this science, and I would like to leave to posterity a documentation as complete as possible. That is why I date everything I do.

Pablo Picasso