Taxonomy of meanings for 則是:  

  • BUT
    • PP+Nab{PRED}.postSbut this is a case of Nab
  • TOPIC MARKER
    • PP+N1{PRED}.postN2{SUBJ}resumptive: these N2, this N2; this fact of N2
    • PP+V{PRED}.postN{SUBJ}as for these N
  • THIS
    • PP+Nab{PRED}.postSAnd this (is of the Nab type)
  • THEREFORE
    • PPadS1.postS2And then in such a way; Since S2, then/therefore S1; Thus
  • THEN
    • PPadS1.postS2THEN + SUCH> then in such a case; then such a person; then; then as for such behaviour; then this is; then this means that; then this leads to [Note that this is not claimed to be a word, just a collocation which it is useful to study.]
    • PPadS1.postS2shi=nonreferentialthen [I collect here the cases where I have so far not found it plausible or easy to attribute to shì a clear anaphoric reference.]
    • PPadS1.postS2referentialthen that concrete item...