[...] Structuralism, as the term suggests, is concerned with structures, and more particularly with examining the general laws by which they work [...] structuralism proper contains a distinctive doctrine which is not to be found in Frye: the belief that the individual units of any system have meaning only by virtue of their relations to one another. This does not follow from a simple belief that you should look at things 'structurally'. [...]
on Northrop Frye. basically means that things in the poem ONLY matter re: how they relate to each other, and not as concepts in their own right ... you could replace any pairwise elements with others that have similar relations to each other and get the same structural reading, as long as you preserve relations between units, which is ofc troubling