Eighty years ago, in a letter to John Quinn, that benefactor in so many ways of the Irish Literary Revival, Yeats wrote that 'if Finvara, that ancient God, now king of Faery', were to offer him a gift, 'I would say, "Let my plays be acted . . ." ' In spite of, and perhaps because of, the recognition that Yeats has received as a major poet, his wish is still largely unrealised. Thus A. S. Knowland's critical guide to those plays of Yeats that appear in Collected Plays does have an emphasis on their theatrical viability. He studies each play, dividing them between the lour stages in the playwright's development, Early Stages, Plays of Transition, The Central Achievement, and Last Stages, as well as adding an Epilogue, and including a postscript about one play not in Collected Plays, but which should fairly be discussed in a volume of this nature, Where There is Nothing.