JOSEF HERMAN'S CREDO. Art, Josef Herman insists, has to do not so much with aesthetics as with conscience. `Without your conscience,' he says, `there exists no awareness of life. Your conscience makes for you a choice what is wrong and what is right in life.'

I had somehow expected Josef Herman to be a large man. But when this Polish-born British painter opened the front door of his terraced West Kensington house and showed me down steep stairs to his cluttered studio, he turned out to be slight. My expectation was undoubtedly born of the monumentality of his art. His archetypical image is of the workingman, particularly the Welsh miner (today almost a vanished species), portrayed on a giant scale. I ask him about monumentality. Is it essential to his art?

``Very much so,'' he says. ``You see, ... there is a certain misunderstanding about monumentality - that one always associates it with physical scale. But true monumentality has, rather, a spiritual ingredient independent of physical size. So a drawing of four inches can be big, while a painting of three yards can be very small.''

The monumentality of Herman's vision is integral, whether he is painting Mexican peasants, Scottish fishermen or landscapes, a bunch of poppies, or the female nude. This last is a current preoccupation, as witnessed by the unfinished paintings crowding his studio walls.

He shows me a ``diary'' - a sketchbook filled with intense drawings of his model. The process of turning the transitory nature of drawings, often quite fiercely expressive and spontaneous, into the monumental symbolism of his paintings, epitomizes this 77-year-old artist's aims. As he has put it: ``I always desired the timeless moment when life stands still and is endless, and this endlessness I tried to paint.''

It was the 11 years (1944-55) he spent living in the Welsh mining village of Ystradgynlais that ``consolidated'' his ``attitude to the human figure,'' he says. One initial, momentary image during his first day visiting the village was so strong that it became the source of his work for years after. In his book ``Related Twilights'' he recalls vividly that image:

``Unexpectedly, as though from nowhere, a group of miners stepped onto the bridge. For a split second their heads appeared against the full body of the sun, as against a yellow disc - the whole image was not unlike an icon depicting the saints with their haloes. ... The magnificence of this scene overwhelmed me.''

Sometimes described as ``Expressionist,'' Herman's art has always been a search for permanence - a poignant fact in the face of a life which has had more than its share of displacements, since his birth into a Warsaw cobbler's household. His preference was always for the quieter Flemish Expressionists, who were ``concerned with the long-lasting involvement of your emotions,'' as he puts it, rather than the immediate, gestural character of the German Expressionists.

Herman's interest in workers as a subject is not folksy or illustrative. His aim has been to find ``the elements which make human life survive. After all, the thing that is basic to our existence is our labor.''

Endurance is an idea never far from the spirit of Herman's work. It is intertwined, surely, with his being Jewish. As a young Polish Jew he found himself a refugee, first, in Belgium and, then (via France) in Britain. Glasgow was his first British home. While there, he made a remarkable group of tragicomic drawings recalling Jewish life in Warsaw. It was in Glasgow, too, that he learned his entire family had been destroyed by the Nazis.

CRITICS have often observed the underlying sense of the tragic in his art, though in meeting him it is the warmth of an outgoing, direct, even exuberant individual that first strikes you.

He takes me upstairs to see his canvas ``Lear Destroyed,'' a painting from the early '60s. Clearly, this is a painting that has deep associations for him. It is Herman's, rather than Shakespeare's Lear - a king ``intensely alone,'' the Fool distant on the horizon playing a flute, indifferent, like nature, to Lear's fate. The glowing redness of twilight - not the drama of a storm - pervades.

Herman mentions quietly his self-identification with Lear. Actually, like all deep art, this ``human bundle,'' as he has called it, lying in the painting's foreground, has an element of self-portraiture.

Herman's ``Lear,'' like most of his paintings, has the weight and mass of sculpture. Has he ever worked as a sculptor? No, he says. When sculptor friends - he particularly admired Sir Jacob Epstein - urged him to, he always replied, ``I prefer to make my sculpture on paper!''

But shelf after shelf in his house displays his vast collection of small African carvings. He picks up a Dogon figure three inches high. ``Isn't it beautiful?'' he says. It perfectly illustrates what he has been saying about scale and monumentality. These African sculptures, he adds, ``are good companions and my `Old Masters.'... I never strive to get anything of their formal ideas or their human content into my own work.''

Intuition is a strong element in his painting. He finds that no image works until his ``sense of rightness'' takes over from his ``intentionality'' as he paints.

Herman is opposed to the idea that ``art is for pleasure.'' He says, ``The aesthetics of art have for years been very much exaggerated.'' Art, he insists, has to do not so much with aesthetics as with ``conscience.''

``Without your conscience, there exists no awareness of life,'' he says. ``Your conscience makes for you a choice what is wrong and what is right in life.'' In his hierarchy of values for art, Herman says, he places ``morality'' much higher than ``aesthetics.''

Thus his subject of workers: In this he sees morality. His conscience is exercised by the inequality of rich and poor. ``It's a matter of which way your conscience drives you - what is for you more important.''

He pauses for a moment. ``And, frankly,'' he adds, ``I am closer to a donkey than a Rolls Royce.