Two poets in a cloud of unknowing; Ways of Light, by Richard Eberhart. New York: Oxford University Press. $11.95 .; Being Here, by Robert Penn Warren. New York: Random House. $8.95.

Ours is not an age of certainties. In our time physicists have discovered the principle of indeterminacy. Modern musicians have explored atonality and dissonance. Poets have entered the cloud of unknowing.

Their unknowing is not a pose. It is in earnest. Here are two poets -- elder statesmen among their kid -- widely traveled, widely acquainted, widely read, at the far edge of long careers, and both staring with hard, clear eyes at the Sphinx. The enigma and its variations. I salute the spirit of life, and I rejoice In one glimpse of timeless truth, The wildness of the thicket, the order of the garden, And the apples, O the red apples of the orchard, Symbol of the rich heart, the unresolved enigmas of man.

So writes Richard Eberhart in his latest volume, "Ways of Light," and going still further, in one of his finest new poems, he clarifies his bafflement: The thinking man, the man of feeling alone With a sense of kindness, love, and justice, Is hard put to it to make sense of existence, As if all the wisdom of the world were nothing . . .

Another major American poet, Robert Penn Warren, puts the problem this way in his new book, "Being Here": The world Is the language we cannot utter. Is it a language we can even hear?

These are lines from a poem whose subject is "Language Barriers," but in poem after poem, Warren probes past and present for answers to his question, "What kind of a world is this we walk in?"

Both Eberhart and Warren are, to be sure, men of the world. They live in a world that includes cocktail parties, dinners given to honor the Sitwells, picnics en famille,m camping trips, visits to the slums, where "the tenements shoulder each other for mutual support" (Warren). These subjects make up the broad spectrum of their poems. But both are also given to lonely nights when the owl cries "Who?" or to moments alone in a rowboat when, somewhere off where seals were on half-tide rocks a loon's cry from beyond the human shook my sense to wordlessness. (Eberhart.)

Each poet is always approaching the moment of epiphany -- the moment when the picture clicks into place -- and each is always finding that the truth is never unambiguous.

Warren gives a denser feeling of ambiguity. In these late poems, he dwells on his Southern past, his memories, as if in quest of his elusive identity. In the end it comes down, for Warren, to this: Put your lands and recollections In order . . . For you, alas, are only Recollections, but recollections Like a movie film gone silent, With a hero strange to you And a plot you can't understand.

Eberhart makes a more mystical matter of his puzzlement. He calls more than once on his mentors, on Plato, Sophocles, Shakespeare, Blake, Dostoevsky, and "my friend Angelus Silesius," as well as on a strange bird that stood once, baffled and dazed, on the poet's porch, after striking a glass door head-on, to teach him "acceptance of irrationality."

Acceptance, yes, and love, these are what both poets count on. But sagacity, that's a scarcer plant. Eberhart and Warren both muster the admirable frankness to admit that years, honors, attainments, have brought neither wisdom nor certitude, but only wonder, always wonder, and more questions.

Perhaps that is what has kept them writing at the peak of their powers into the sixth and seventh decades of life.