Richard Greenberg ponders fascinating issues in this intellectually bracing drama, asking, among other things, what is the source of inspiration? And what's the difference between creative brilliance and mental illness? He never actually answers the questions but allows the audience to draw its own conclusions on the basis of the evidence presented over two acts, the first about three troubled adult children of famous architects, the second about the architects themselves. Greenberg's writing is polished and witty, but the play itself is cold as a doctoral thesis, especially in this Actors Revolution Theatre production: the three performers don't really know how to reveal the feelings swirling beneath Greenberg's highbrow jokes and Ivy League references. Through 9/18: Thu-Sun 8 PM. Steep Theatre, 3902 N. Sheridan, 773-531-9079. $15-$20.