OK so this is hardly a quote. But it has intrigued me ever since, as an eleven year old, I came upon it in my first French text book, at Woodside Senior Secondary School, . Glasgow.   It was accompanied by a drawing which served to explain the seeming circular  nature of the piece.  My lack of drawing skills prevents me from replicating the small sketch.   But it’s an easy read for those with more than an elementary knowledge of the language. 

Je  suis ce que je suis.

Je ne suis pas ce que je suis.

Si j’etais ce que je suis,

je ne serais pas ce que je suis.