Sentence:  In lieu of this opposition, the lecture speaks of a “substantive <WSD>tropology</WSD>” of love, where "tropology" means more than a decorative interplay of tropes; it signifies the ability “simultaneously to capture the real analogy of sentiments and the power of "eros" to signify and express "agape"." 
Meaning of the word marked with <WSD> tags:  A recurring motif or metaphor, a trope; an interplay of tropes.