Perhaps the Proximity people thought that they had got round that little problem by giving the same definition for each of the items in the list; but we know that only very rarely are two synonyms bi-unique (which is another way of saying that if A = B, B does not necessarily always equal A), an ineluctable fact of language.
( ( ( ( ( Perhaps ( ( the ( Proximity people ) ) ( thought ( that ( they ( had ( got ( ( round ( that ( little problem ) ) ) ( by ( ( giving ( the ( same definition ) ) ) ( for ( each ( of ( ( the items ) ( in ( the list ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ; ) but ) ( we ( ( ( ( know ( that ( ( only very ) ( rarely ( are ( ( two synonyms ) bi-unique ) ) ) ) ) ) ( -LRB- ( ( which ( is ( ( another way ) ( of ( saying ( that ( ( if ( A ( = B ) ) ) ( , ( B ( ( ( does not ) necessarily ) ( always ( equal A ) ) ) ) ) ) ) ) ) ) ) ) -RRB- ) ) ) , ) ( ( an ( ineluctable fact ) ) ( of language ) ) ) ) ) . )
(ROOT (S (S (ADVP (RB Perhaps)) (NP (DT the) (NNP Proximity) (NNS people)) (VP (VBD thought) (SBAR (IN that) (S (NP (PRP they)) (VP (VBD had) (VP (VBN got) (S (VP (VB round) (NP (DT that) (JJ little) (NN problem)) (PP (IN by) (S (VP (VBG giving) (NP (DT the) (JJ same) (NN definition)) (PP (IN for) (NP (NP (DT each)) (PP (IN of) (NP (NP (DT the) (NNS items)) (PP (IN in) (NP (DT the) (NN list)))))))))))))))))) (: ;) (CC but) (S (NP (PRP we)) (VP (VBP know) (SBAR (IN that) (S (NP (RB only) (JJ very)) (ADVP (RB rarely)) (VP (VBP are) (ADJP (NP (CD two) (NNS synonyms)) (JJ bi-unique))))) (PRN (-LRB- -LRB-) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (NP (NP (DT another) (NN way)) (PP (IN of) (S (VP (VBG saying) (SBAR (IN that) (S (SBAR (IN if) (S (NP (NNP A)) (VP (SYM =) (NP (NNP B))))) (, ,) (NP (NNP B)) (VP (VBZ does) (RB not) (ADVP (RB necessarily)) (VP (ADVP (RB always)) (VB equal) (NP (NNP A))))))))))))) (-RRB- -RRB-)) (, ,) (S (NP (NP (DT an) (JJ ineluctable) (NN fact)) (PP (IN of) (NP (NN language))))))) (. .)))
Just because x equals y, you can't assume that y and x are always identical.
( ( Just ( because ( x ( equals y ) ) ) ) ( , ( you ( ( ( ca n't ) ( assume ( that ( ( ( y and ) x ) ( ( are always ) identical ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (RB Just) (IN because) (S (NP (SYM x)) (VP (VBZ equals) (NP (NN y))))) (, ,) (NP (PRP you)) (VP (MD ca) (RB n't) (VP (VB assume) (SBAR (IN that) (S (NP (NP (NN y)) (CC and) (NP (SYM x))) (VP (VBP are) (ADVP (RB always)) (ADJP (JJ identical))))))) (. .)))