Ferlinghetti's work challenges the definition of art and the artist's role in the world.

Her work challenged concepts of sexuality, culture, and artistic production.

He began in the 1960's as a playwright whose work challenged the Communists' hold over the country.

But this work is really about challenging the way we interact with technology.

His most recent work challenges the widely-held economic theory of growth.

Her work challenges the reader to think about how they affect their environment.

More importantly, his work challenged and inspired those who followed.

It had been true, and he often reflected, the work was challenging.

Their work radically challenged the very definition of what a finished picture could be.

After 50 years, his work still challenges the eye.