This reissued book is one of the key works that influenced and shaped the contemporary evaluation field. The book developed a new, expanded conception of the validity of evaluation studies, based on broad criteria of truth, beauty, and justice. It also presented a widely-used typology of evaluation approaches and critiqued these approaches with the validity criteria. Its long term influence is demonstrated by the book, (published in 1980) and criteria being prominently featured in the overall theme for the forthcoming American Evaluation Association's annual conference in November, 2010.