Isleworth Mona Lisa
According to Leonardo's early biographer Giorgio Vasari, Leonardo had started to paint "Mona Lisa" in 1503, but "left it unfinished". However, a fully finished painting of a "certain Florentine lady" surfaced again in 1517, shortly before Leonardo's death and in his private possession. The latter painting almost certainly is the one that now hangs in the Louvre. Based on this contradiction, supporters of the authenticity of the "Isleworth Mona Lisa" claim it is the unfinished "Mona Lisa", made at least partially by Leonardo, and the Louvre "Mona Lisa" a later version of it, made by Leonardo for his own use.
Vincenzo Peruggia
There are currently two predominant theories regarding the theft of the "Mona Lisa".
Peruggia said he did it for a patriotic reason: he wanted to bring the painting back for display in Italy "after it was stolen by Napoleon". Although perhaps sincere in his motive, Vincenzo may not have known that Leonardo da Vinci took this painting as a gift for Francis I when he moved to France to become a painter in his court during the 16th century, 250 years before Napoleon's birth.