Medieval illuminations are a rich source of fool imagery, sometimes deploying the fool for serious theological messaging, at others apparently due to mere whimsy on the part of the illuminator. Of the former, most common are depictions of a fool to illustrate the opening verse of Psalm 53:
The fool says in his heart ‘There is no God’.
Dixit insipiens in corde suo non est deus.
In this example, dated after 1205, the Master of the Ingeborg Psalter has the God-denying fool hold a scroll proclaiming this in Latin, Non e[st] Deu[s] (There is no God). To drive home the point, there are two demons encouraging him in his heresy, and a single angel seeking to deter him from pursuing it.
See also a rare (and possibly unique) example of an illumination illustrating this foolish heresy in Psalm 53, using a historical jester as the fool. This gives us a double portrait of Henry VIII and his real-life fool Will Somers, featured in the king’s own Psalter.
Credit: Master of the Ingeborg Psalter (French, fl.c. 1195-c.1210), Initial D: The Fool with Two Demons (after 1205), illumination, tempera colors and gold leaf; The J. Paul Getty Museum, Los Angeles, Ms. 66, fol. 56, 99.MK.48.56, public domain