Last May, inside a small recital hall, I watched as 10 dancers under the age of six balanced tall peacock feathers in their palms. They wore pink silk tunics and flowers in their hair (the sole boy in the group wore green) to celebrate 16 weeks of training as “Duncan dancers.” How I landed at this recital involved four years of parenting (my daughter was among the performers) and more than a century of Isadora Duncan’s artistic influence on the world.

Duncan is often described as the mother of modern dance, a legacy eclipsed by the more sensational details of her personal life. For the young Duncan dancers on stage, it mattered little that Duncan, born in 1877, had been—among other things—bisexual, an atheist and a communist sympathizer, or that she adopted six of her female d...