Stefan Buijsman (b. 1995) graduated with a master’s degree in philosophy from the University of Leiden at 18 years of age, after which he left for Sweden to pursue a Ph.D. He completed the four-year doctorate program within a year and a half, making him one of the youngest Ph.D.s ever. At present, he is studying the philosophy of mathematics as a post-doctoral researcher. Together with Govrien Oldenburger, he wrote the children’s book The Counting Kingdom.