Guido de Ruggiero (1888-1948) was perhaps the greatest Italian intellectual historian in the twentieth century. He was a fierce champion of liberalism, an ardent opponent of Fascism, an insightful critic and interpreter of his contemporaries, and a formidable philosopher in his own right. Idealism & Experience: The Philosophy of Guido de Ruggiero comprises eight new critical essays, as well as English translations of five of de Ruggiero's most important shorter writings, which chart the development of his thought between 1914 and 1946. Taken together, these essays reveal the range, richness and philosophical sophistication of de Ruggiero's ideas, enabling Anglophone readers to appreciate their enduring relevance in our own troubled times.