If there is a "design" (overall structure or form) in TWL it was either
put there by Ezra Pound, not composed by Eliot or imposed _after_ the
fact by Eliot as he wrote the notes. If you want to assign a "design" to
Eliot himself, you have to find it in the original typescrpt as we see
it in the fasimile edition. Probably Eliot himself was not free of the
19th-c superstition that a poem must have an "organic" form, and this
shows up both in his desire to preface Gerontion to the poem and in the
notes he wrote, particularly the note on the poem being what Tiresias
saw! That Eliot did in fact share this critical error is shown by his
silly remark that Hamlet was an artistic failure!

There is much to be said for the argument in an essay in Critical
Inquirry some decades ago entitled, "Coherent Readers; Incoherennt
Texts."  And this seems to apply quite felicitously to TWL. The
coherence which many critics find in the poem is there all right --
because they put it ther!

This is NOT the same as saying a poem can mean anything a reader wants
it to mean. There still remains a need for responsible reading (if the
critic wants anyone to pay attention to him/her anyhow).  If some reader
were to 'find' in TWL a deliberate point-by-point refutation of Hobbes's
_Leviathan_ or of Kant's Critique of Pure Reason we (or at leas I)
wouldn't argue with the reading, I would merely ignore it and anything
else which that particular critic wrote. (As I do simply ignore the
readings of several posters on this list.)  But though not anyy old
reading some reader wants will do, the range of possible conflicting but
legitimate readings is, I think, fairly wide, and rather wider in the
case of The Waste Land. And I would argue that withiin that range is one
that Eliot himself specifically rejected with a sneer: that it expressed
the disillusion of a generation! When WW 1 began, Henry James commented
something like, So this is what it all meant, by which I presume he
referred to the whole self-satisfaction of the end of the 19th-c that
"civilization" had been achieved, that Progress was a metaphysical
reality, and that (as expressed in Kipling's "White Man's Burden") that
achieved civilization had only to be imposed on the rest of the world
that still lay in outer darkness.

I think we are in Rat's Alley: The war to end war has instead been a war
that itself never ended, and "we" the postwar generation  are still, as
we walk through the streets of London,  in the trenches ourselves. (That
third who walks always beside 'you' might welll be the unburied dead of
the endless war.)  One is reminded of The Cabinet of Dr. Caligari. (That
closed car at four: where is it going anyhow?)  And had Eliot persuaded
Pound to allow him to preface Gerontion to TWL, the corridors of
Versailles (the cunning passages) could be the twisted streets of London
and both could be the intricate maze of the trenches of that war that
will not end, the dead flowing over London Bridge in an endless stream
(I had not known death had undone so many: it is difficult to believe
the death toll of WW1). And so forth, the poem is an echo chamber. One
would not want many poems with that sort of polysemy. I am glad we have
one like this though.