Professor of art history at the University of Bonn, he wrote three major critical biographies: of Johann Joachim Winckelmann, of Diego Velázquez and of Michelangelo.
Born in Marburg, Justi studied theology at the University of Berlin before transferring to philosophy.
He graduated in 1859 with a thesis 'Über die ästhetischen Elemente in der platonischen Philosophie'.
[2] Justi established his reputation with a three-volume work on Johann Joachim Winckelmann.
[3] He succeeded Anton Springer in the chair of art history at the University of Bonn,[4] holding the post from 1872 until 1901.