At the new Whitney Museum in New York early this summer I came across the Guerrilla Girls for the first time.

This anonymous art group set themselves up in the 1980s to protest inequality in the art world - and they celebrated their 30th anniversary this year. Members of the group don guerrilla masks and do provocative, but humorous, stunts to protest sexism and racism in art. One theme is the missing voice of women in art shows by the big name museums. (See one of the group’s early posters below.)

The group's message came to mind a few weeks ago when I saw two wonderful shows by women artists at the Tate Galleries in London: Agnes Martin and Barbara Hepworth. Their work had such refreshing and energizing sensibilities. Kudos to the Tate.

Described as an abstract expressionist, Martin’s work felt like something I’d never seen before. Hepworth’s sculpture was done in Cornwall and when I went to Cornwall a few days later I was struck by the magical way she had captured the light and landscape there.

The exhibits left me pondering what I’d missed out on as a result the missing voice of women in art. The same is true of films and literature, of course. There's so much value in diverse perspectives.