Born in Hadamar, a town of Hesse, Karl Wilhelm Diefenbach in the fall of 1872 moved to Monaco of Bavaria to enter the Academy of Art in the city. This was the period in which the painter was inspired by the movement of the "Sturm und Drang", spread to most of Germany; the encounter with many intellectuals dedicated to the worship of nature and the research in the field of folklore soon led him to leave the aristocratic environment where he spent several months between 1873 and 1874 employed by the Duke of Nassau.
Following a period of illness that led him to a careful reflection on his life, he devoted himself, including by means of painting, to the preaching of universal peace and the return to nature; the speech "On the origins of human misery" caused him to a term of imprisonment followed by a smear campaign supported by the authorities of the time.
The painter, in order to escape the intolerable climate that was created and to continue its activities in full freedom, decided to move to Höllriegelsgereut, where in 1887 he met the German painter Hugo Höppener said Fidus (1868-1948) who became his devoted student. Despite the continued persecution Diefenbach, supported by a wide array of intellectuals, had the opportunity to exhibit their work in 1889 and in 1891 in the city of Monaco with a great success.
Summoned to court by the Emperor Franz Joseph in 1892 the painter came to Vienna, a city which soon leaved because not accepted by the authorities due to its unconventional character, settling at first in the vicinity of Cairo and finally in Capri where he had a renowned studio, frequented by intellectuals and artists from the island.
In the Certosa di San Giacomo (the Museum dedicated to Karl Wilhelm Diefenbach, in Capri) are preserved many of his works of the period “caprese”.