The reading and writing of letters is a frequent and favourite subject, not only in the genre paintings of Gerhard Terborch, but in the work of many other seventeenth-century Dutch artists. However, the quiet conviction of this particular rendering of the theme makes it much more than a repetition of an acceptable formula. It is something more, also, than a convenient peg on which to hang the artist's considerable skill in painting different textures - paper and wood, cloth, fur, softness of skin and smoothness of hair, and the splendidly suggested weight and weave of the table carpet thrown back as if to prevent its interfering with the young ''lady's'' concentration. These textures are modulated by a gentle light, from an unspecified source, which seems designed to show them off to their best advantage rather than to draw attention to itself. Indeed, light, as such, is rarely one of Terborch's main interests as it is for Vermeer and De Hoogh, his contemporaries. Terborch uses it functionally, to illumine the men and women who are stage front in his otherwise dark pictures; and it is they who are his chief concern.
His attention and penetrating observation are brought to bear on the inner motivations of his protagonists. The viewer's eye is immediately drawn, in ''Lady Reading a Letter,'' to the eyes of the girl and the intimate pleasure they express in the words she is reading. Her whole face, in fact, seems an affectionate response to the piece of paper held so delicately in her fingers. Christopher Brown, writing about another Terborch painting (of an officer dictating a letter), observed that writing and reading letters in Dutch seventeenth-century paintings often ''signify absent love.'' He goes on, ''The inscription accompanying a letter-writing Amor in Otto van Veen's Amorum Emblemata (Antwerp 1608) reads: 'Just as, for lovers, pictures even of absent loved ones are delightful . . . how much more delightful are letters, which convey the true imprints and marks of a lover.' '' These words might justifiably have been inscribed on the back of ''Lady Reading a Letter.''
Terborch, though he was well travelled (going to Italy, France, Germany, Spain and England), gives in his paintings little evidence of influences outside of the Holland of his day, and even in Holland he seems to have mixed with other artists hardly at all after his initial training. From 1654 until the end of his career in 1681, he lived and worked away from the artistic centres of his country, in Daventer. His early work was in the tradition of barrack room scenes. Though he progressed from such ''low-life'' subject matter to pictures of more well-to-do, bourgeois types of people, he never lost interest in what might be called ''the event.''
One only has to compare ''Lady Reading a Letter'' with a Vermeer of a similar subject, ''Lady Reading at an Open Window,'' to observe how much more intrigued Terborch was by the feelings and emotions of people. Between Terborch's lady and her letter there is an undemonstrative but clearly evident love affair. Something of significance to the girl is happening. Vermeer's lady also concentrates intently on her letter, but her reactions are hidden from us by her lowered eyes as well as by the fact that the artist seems to have deliberately suppressed any sign of feeling at all. Unlike Terborch's lady, she and her surroundings are not differentiated: she is an object in a room of beautifully arranged objects. Terborch is sometimes accused of painting ''doll-like'' figures - but in truth Vermeer's lady is far more like a mannequin than his. The light from the window in Vermeer's painting may be used by the lady to illumine her letter, but the same light falls without discrimination on letter, dress, face, wall, curtains, bowl of fruit - all part and parcel of one thing: that ''thing,'' so wonderfully painted, being Vermeer's own sight. His paintings represent how he sees quite as much as what he sees.
The slightly disturbing aspect of this comparison (if you happen to think that Vermeer's art is of a much higher calibre than Terborch's) is that the Terborch not only makes the Vermeer look contrived, it also points up the dispassionate character of Vermeer's vision as being not entirely positive. It is as though his self-contained visual world was so consciously objective in its harmonies that the human heart could not be allowed to disturb it.
Terborch, who aptly enough was also a portraitist with a keen eye for character, obviously thought otherwise.
And it is instructive that the French nineteenth-century analyst of Dutch art , Eugene Fromentin, who enthused at length about Terborch, seemed to think that Vermeer was nothing more than an oddity. In fact, Fromentin is a little self-contradictory when he maintains that ''the great Dutch school'' - to its credit - ''thought of nothing but of painting well. It was satisfied to look around and to do without imagination'' and that it was an art without ''motive, '' without ''subject,'' and even without ''the gifts of heart and mind, sensibility, tenderness, generous sympathies for the dramas of history.''
It is true that neither Terborch nor Vermeer painted battle scenes or romantic anecdotes, but to claim admiringly that ''Holland has not imagined anything, but . . . has painted miraculously well'' and yet not to appreciate Vermeer seems incomprehensible. He, if anyone, is a brilliant painter with a subdued imagination. And to relish Terborch's ''smooth, simple, clean, limpid'' painting without noticing how he is continually capturing the small sensations of human thought and motive, and using his imagination to perceive and present them, is puzzling.
All the same, it is Fromentin's tribute to Terborch which still outclasses any other appreciation of his individuality and talent. He describes his art as ''an art which adapts itself to the nature of things, a knowledge that is forgotten in presence of special circumstances in life, nothing preconceived, nothing which precedes the simple, strong and sensitive observation of what is.''