The new golden rule for playwrights is: the less comprehensible, the better. Caryl Churchill’s short A Number is as fine a specimen as an audience seeking bamboozlement could wish. At the premiere, I spotted many a closed eye: rapture or somnolence? But 65 minutes later, at ovation time, the response was tumultuous. Salter (Sam Shepard) has three sons: Bernard No. 1, age 40, Bernard No. 2, age 35, and Michael Black, also 35, but not a twin (all played by Dallas Roberts). The auditorium has been reconfigured as a steep arena; the small acting area has a black leather couch, a dim lamp, and a dark brick wall with a door in it. Salter mostly sits, while the sons come and go serially, to sit, pace, hang upside down, or lie on the floor, apparently at director James Macdonald’s whim. Salter seems to have lost his wife and son in an auto accident. Or not: The wife may have committed suicide. He has also cloned the dead son, resulting in three or twenty-odd new ones. One is namby-pamby, one sinister, one regular. One may have killed another; Salter may have been a bad father. The fragmented dialogue interrupts, overlaps, illogically completes. Typical sentence: “Because this minute we sit here there’s somebody a lot of them but think of one on the electric bedsprings or water poured down his throat and jump on his stomach.” Contradictions sprout instantly, or only slightly delayed. Ms. Churchill certainly does a number on us.