A poem, a contradiction . . .

     One strategy for proving a mathematical theorem is a "proof by contradiction."  In such a proof one begins by supposing the opposite of what is to be proved -- and then reasons logically to obtain a statement that contradicts a known truth. This contradiction verifies that our opposite-assumption was wrong and that our original statement-to-be-proved is indeed correct.   (An easily-read introduction to "proof-by-contradiction" is given here.)
       Peggy Shumaker is an Alaskan poet whom I had the pleasure of meeting at a reading at Bloomsburg University where I was a math professor a few years ago.  Her poem, "What to Count On," below, has a beautiful surprise after a sequence of negations -- and reminds me of the structure of a proof-by-contradiction.

What to Count On     by Peggy Shumaker

Not one star, not even the half moon       
       on the night you were born
Not the flash of salmon
       nor ridges on blue snow 
Not the flicker of raven’s
       never-still eye 
Not breath frozen in fine hairs
       beading the bull moose’s nostril
Not one hand under flannel
       warming before reaching
Not burbot at home under Tanana ice
       not burbot pulled up into failing light
Not the knife blade honed, not the leather sheath
Not raw bawling in the dog yard
       when the musher barks gee
Not the gnawed ends of wrist-thick sticks
       mounded over beaver dens
Not solar flares scouring the earth over China
Not rime crystals bearding a sleek cheek of snow
Not six minutes more of darkness each day
Not air water food words touch
Not art
Not anything we expect
Not anything we expect to keep
Not anything we expect to keep us alive

Not the center of the sea
Not the birthplace of the waves
Not the compass too close to true north to guide us

Then with no warning
       flukes of three orcas
                 rise, arc clear of sea water

I found Shumaker's poem at PoetryFoundation.org.  It also is included in her collection Underground Rivers (Red Hen Press, 2002).