head painted on the right wing of the Trinity Altarpiece show a similar realism in the treatment of portraits by van der Goes. The Portrait of a Man at Prayer with Saint John the Baptist (Walters Art Museum) shows similar traits. As at the time the display of strong emotion in public was frowned upon, Hugo van der Goes resorted in this work to the most subtle facial expressions to express his sitters' mental state. In the Portrait of a Man at Prayer with Saint John the Baptist the deep concentration of the sitter is suggested in a subtle manner in the raised eyebrow and tense muscles around his mouth. Stylistic development Van der Goes is regarded as one of the most original and innovative early Netherlandish artists. As many works of van der Goes have not survived and most of the surviving works cannot be dated accurately, it is difficult to establish a stylistic development for van der Goes. The Portinari Altarpiece is the sole of his works that can be confidently linked to the artist. Even so, art historians see a global development starting with a style close to the illusionism of van Eyck. This early style was characterised by a detailed description in rich colour and a single vanishing-point perspective as can be observed in the Monforte Altarpiece and Portinari central panel. Van der Goes may have learnt this style from Petrus Christus or Dieric Bouts. Later works gradually abandoned illusionism for an increased emphasis on the artificiality of the picture as created image, divorced from reality. This effect was achieved by the use of a limited range of colours and the expressive distortion of figures as well as space. Example of works in this later style are the Death of the Virgin (Groeningemuseum, Bruges) and the Adoration of the Shepherds (c. 1480, Gemäldegalerie, Berlin). Other characteristics imputed to these later works are a breakdown of space, a renunciation of still-life elements not directly related to the subject matter and an exaggerated agitation and an excess of expression in the figures. Early scholars saw the evolution as a reflection of the increasing mental instability of the artist. Later interpretations gave much weight to the artist's adherence to the Modern Devotion movement as an important influence. These interpretations see the later paintings as attempts by van der Goes to translate the ideas of this movement into a visual