David Jozef Wijnkoop was a son of rabbi Jozef David Wijnkoop. He studied Dutch philology at the Municipal University of Amsterdam. As a student, he became a member of the SDAP. After his BA examination, he cut short his studies and became a propagandist for the party. He disagreed with the more moderate (revisionist) direction followed by the leadership of the party. In 1907, he co-founded the mar…