Artistic sensibility is one of the most difficult things in the world to define. It cannot be measured or pinpointed with any degree of accuracy. It is elusive; in fact it remains invisible to all except those who share it to some degree. It cannot be learned, taught, or explained, and anyone who lacks it will almost certainly deny that any such thing even exists.
It can, however, be stimulated and awakened. Not perhaps to the degree some of us would like, but still enough to enable those so ''awakened'' to become better artists or to appreciate art more deeply.
To develop sensibility requires cultivation and constant care. Since it is as much a matter of intelligence as of feeling, and is a living and dynamic process rather than a passive quality or state, it must be exercised, stretched, and kept alert or it will remain immature and unrealized - or possibly even wither away and die.
How this can be done varies from individual to individual. For some, this awakening results from greater exposure to art; for others, it can simply be a matter of learning what paint, ink, clay, can do. Then again, it can result from the attentions and the suggestions of an exceptionally caring and intuitive teacher or friend - or from a profoundly moving personal experience that alerts the individual to levels and dimensions of experience hitherto unknown.
It can also come from age and experience, or from the wish or the need to live a richer inner life. But, from whatever its source and regardless of whether it takes the form of increased creativity or heightened sensitivity to art, it can only be felt as an enhancement of life.
Artistic sensibility stems more from an intuitive awareness of the quality and value of life than from an insight into its nature and significance. It doesn't so much understand life as recognize its preciousness. As such, it is fully aware of the fragility and tenuousness of human life, and of man's vulnerability to fears and anxieties pertaining to his existence and survival.
It is not, however, exclusively concerned with life's preciousness and vulnerability, for it has been known to revel in life's fullness and vitality (Rubens); its muted harmonies and nuances (Chardin); its ability to dignify (Rembrandt); and its enigmas and paradoxes (Goya). It is as varied as human nature and as individual to each and every one of us as our fingerprints and handwriting.
The child of six, for instance, splashing away with paint, hesitating, and then daubing red paint onto a picture, is very likely exercising artistic sensibility, albeit on a very primitive level. The step from that to a Redon putting a final touch of coral pink at precisely the right spot in a painted floral, or a Calder deciding that a small supporting chain in a mobile should have six links instead of seven, may be tremendous, but is still closer than one might think.
In both instances, sensibility makes itself known through an impulse to do something one way and not another. For the child, this may result from nothing more complex than the feeling that a few touches of red would look good next to green - or upon a field of yellow. To a Redon or Calder, however, such an impulse or ''decision'' is only one of hundreds made during the creation of a work of art. To a child of six, sensibility is probably a quite unconscious matter. To a highly skilled and sensitized artist such as Redon, on the other hand, it is a well developed and very consciously utilized quality.
To a modernist artist, especially, sensibility is of primary importance, since it is often the crucial element in his art. A painting consisting entirely of geometric or free-form shapes, and of color applied with little or no reference to natural appearance, depends to a great extent on hundreds of tiny and subtle adjustments and relationships of form and color for its meaning, effectiveness, and quality. From Delaunay to Natkin, Soutine to Pollock, Gris to Diebenkorn, sensibility plays an extremely central and crucial role in modern art; to approach the work of these artists with insufficient or misplaced sensibility, therefore, is largely to miss what their art is all about.
But artistic sensibility can also take the form of an extraordinary alertness to the appearance, mood, atmosphere, and structure of nature. An alertness that can take something as tiny as a leaf, or as grand as a mountain landscape, and create an image that both sparkles with life and haunts us with its profound actuality and presence.
Thus, Durer's watercolor drawing ''A Young Hare'' is as full of life and actuality as it was when first painted almost 500 years ago, and Samuel Palmer's early watercolor studies of foliage and fields still overwhelm us with his experience of them over one hundred fifty years after they were painted.
This form of sensibility, however, has not been encouraged during this century, preoccupied as we've been with other matters. But things are changing: an increasing number of younger artists are not only working in this vein, but are also actually receiving critical and curatorial encouragement for their work.
Even so, it is still an uphill battle, especially for someone like Frederick Brosen, whose watercolor cityscapes are just beginning to catch the eye of a few sensitive collectors, and an interested critic or two.
This is partly due to the fact that he prefers to depict the older districts of American and European cities in a manner that seems to reflect seventeenth- to nineteenth-century landscape ideals rather than modernist, photorealist, or even typically ''conservative'' twentieth-century ones. And partly because we as a whole today don't know what to make of contemporary landscapes or cityscapes that aren't basically geometric, coolly photographic, or flamboyantly coloristic and expansive.
Another problem, at least to the ''informed' twentieth-century eye, is that Brosen focuses on the picturesque - a prime painterly ''sin'' in this century. Hadn't Cezanne, after all, made it perfectly clear that it was the intrinsic structure of a view that mattered, not its surface appearance - and most certainly not its historical or sentimental associations? With this in mind, how dare this young man, still in his twenties, paint exquisite watercolors of such places as Notre Dame in Paris, the Amstel in Amsterdam, the Thames from Waterloo Bridge in London, or the upper reaches of Broadway in New York?
The answer, of course, is that Brosen is an original, with the talent, intelligence, creative integrity, and sensibility to do as his spirit dictates. He is not an ''innocent'' painting only what he sees, but is, rather, a highly disciplined and art-historically aware painter who would rather follow his own vision than bend it or his talents to do what is expected of him.
Brosen is one of the increasing number of bright and talented younger artists of today who have, after extensive study and analysis of modernism's goal and ideals, cut themselves off from it entirely. Although that decision doesn't require the courage it would have twenty years ago (thirty years ago it would have been professional suicide), it still is not an easy one to make. And the problem is compounded by the fact that no artist creates entirely by himself; he must, at least to a point, shape his art by drawing upon the wisdom and experience of artists before him. He must, in other words, seek examples and precedents for his art from somewhere.
Brosen chose to study, and to a degree emulate, the art of certain Old Masters, most particularly Claude Lorrain, Canaletto, and Bonnington. This study , undertaken in this country and during a prolonged trip abroad in 1981, has been intensive and specific. As a result, he is becoming increasingly clear about what he wants to do and how he wants to do it.
''Rooftops, Ile de la Cite, Paris'' is a page of a sketchbook made during his European trip last year. Although very small - only 4 1/2 by 6 1/4 inches - it is monumental in conception and in effect. It is also breathtakingly vibrant and alive, and represents, in the truest and simplest sense, what artistic sensibility can do, and what it is all about.