John Constable is best known for his idyllic paintings of the English countryside. Yet he was also a brilliant innovator who brought a new vivacity to the observation of nature. He practiced oil painting in the open air, capturing in particular the 'effervescent' effects of atmospherics - as can be seen, for example, in his wonderful studies of clouds. His art became a benchmark for naturalist painters throughout Europe and America in the nineteenth century, and he continues to be one of the most popular and influential artists to this day. This book draws extensively on the artist's own correspondence to provide a fresh understanding of his artistic aims and achievements, and reassesses his role in the development of modern art.