Just a quick word on Brian Gilmore's notion {letters, Jan. 26} of poetry as nothing more than a spontaneous insight, perfect and final: wrong.

Mr. Gilmore seems to be suffering from an acute case of the moderns. In his zeal to be authentic and spontaneous (to him, one seems to equal the other), he has mistaken the creative process for little more than nerve endings. Asserting that poems are ''natural reactions,'' he has confused a mere burst of expression of feelings with art.

Does Mr. Gilmore really believe that "Paradise Lost" sprang full-blown from Milton's consciousness? That the initial meeting between Romeo and Juliet, a perfect Shakespearean sonnet in rhyme and meter, is the result of a frantic moment of inspiration? Is Mr. Gilmore saying that this poetry required nothing more than scribbling ''feelings'' onto foolscap? No editing, no revision, no painstaking attention to subtle nuances not only of a word's meaning but even of its syllables?

I think that what Mr. Gilmore is talking about is something along the lines of purposely disjointed memoirs or stream-of-consciousness notes to himself. There is nothing wrong with this type of exercise, of course. It may, in fact, be useful in an attempt to learn about oneself. Mr. Gilmore may even, if he likes, call it poetry. Many others, I have to think, would not. CHRISTOPHER COLLINS Washington