One of the reasons why Samuel Beckett's "Waiting for Godot" continues to seem one of the crucial dramatic statements of our era is that it poses the only question about life that ultimately matters to all of us - to wit, what is it all for.

The power and wit of Beckett's ruminations are brought home with lively discernment in "Thunder and Sweet Wine," a sort of piquant variation on "Godot" by the Earth Onion Women's Theater currently in production at the troupe's quarters at 2416 18th St. NW.

Beckett shows us the existential predicament of a befuddling universe as confronted by two complementary main characters, the tramps Didi and Gogo, representing the intellectual and instinctive sides of human nature.In "Thunder and Sweet Wine," these two become women and Didi, moreover, is pregnant.

Aside from this transformation, there is one other major alteration in Beckett's scheme. In place of Beckett's Lucky and Pozzo sequence, which is like an interpolated aria on the theme of slave and master, the female pair in "Thunder" shift their impersonations to Blanche and Stella of "A Streetcar Named Desire," and present an extract thereof.

The concept is an inveigling one and it works dramatically. The backbone of Beckett's lines - as brilliantly pungent as ever - is retained more or less intact. What's new is the psychological perspective, which suggests that the despairing dilemma of modern man takes on revealingly different inflections when seen through the eyes of modern woman.

Jane Le Grand, the troupe's artistic director, plays Didi with wonderful spunk and facility, reaching deep into the "subtext" of the character to give a fine sense of urgency to her words and gestures. Brigit Murray is much less convincing as Gogo, despite the intelligence of her portrayal and the good rapport she establishes with Le Grand - her acting is a bit too evidently synthetic. In a cast of two, this disparity is conspicuous, though it is by no means fatal to the fascination of the performance.

The troupe hopes to extend the run, on Friday and Saturday evenings at 8, through March. Reservations (387-1385) are recommended - the seating space and playing area are so small, an intruder would have difficulty distinguishing actors from audience.