The essays in this volume offer a critique of From Unity to Pluralism: The Internal Evolution of Thomism by Gerald McCool, SJ. Twelve philosophers in this collection analyse key aspects of McCool's interpretation of Aquinas, which stands opposed to the motivating ideals found in One Hundred Years of Thomism: Aeterni Patris and Afterwards , a symposium published in 1981 to celebrate the centenary of Pope Leo XIII's encyclical Aeterni Patris .