This meditation is a translation, by John H. Kok, of D. H. Theodoor Vollenhoven\u27s Spel of ernst? published in the Gereformeerde Kerkbod (11, 18, 25 November and 2 December 1923).—“Wat is Christelijke filosofie?”—as Professor of Christian Philosophy at the Vrije University, Amsterdam. A slightly revised rendition, translated from the Dutch by Dr. Kok, was published in Stuwdam (16 January 1937) under the title Groote kinderen