 One of the earliest to integrate psychology with art history was Heinrich Wölfflin (1864–1945), a Swiss art critic and historian, whose dissertation "Prolegomena zu einer Psychologie der Architektur" (1886) attempted to show that architecture could be understood from a purely psychological (as opposed to a historical-progressivist) point of view.Another important figure in the development of art psychology was Wilhelm Worringer, who provided some of the earliest theoretical justification for expressionist art.The Psychology of Art (1925) by Lev Vygotsky (1896–1934) is another classical work.