X and Y

There are quotes involving functions that take arguments X and Y, and swapping them works. For example,

The relationship between theoreticians and practitioners is based on trust and understanding: theoreticians (X) do not trust practitioners (Y) and practitioners do not understand theoreticians.

Actually, that quote has a couple of (X,Y) pairs!

The book review last Sunday has a review of poems by John Laughlin, a great publisher---he has published James Joyce, Tennessee Williams, Nabokov, Henry Miller, Dylan Thomas---and a ?-poet, and ends with a quote,

"For a poet (X), he was a great publisher (Y), and for a publisher, he was a great poet".