In this chapter, we turn to discourse identification of pro, which is well-known to be topic-oriented (see Givón, 1983; Huang, 1984; Samek-Lodovici, 1996; Grimshaw and Samek-Lodovici, 1998; Frascarelli, 2007; Camacho, 2011; Sigurðsson, 2011). We will study two separate cases: instances in which pro is identified by inflection and also by a topic, and cases in which pro is identified only by a topic. In order to understand the discourse conditions of pro, we will review Frascarelli's (2007) proposal for Italian. This will lead me to reassert Rizzi's double requirement of licensing and identification, recast in terms of valuation and discourse linking. I will then present cases within NSLs where morphological valuation fails, and only topic linking applies. Then I will turn to obligatorily overt subject languages with limited cases of NSs (topic drop), and after that I will review Chinese-type discourse NSLs. Finally, I will develop the analysis that one of the relevant differences between agreement-based and discourse-based NSLs relates to pro's specification.

Topics and pro

A number of researchers have noted that pro is topic-oriented. Samek-Lodovici (1996, 29) explicitly states that NSs must be licensed by topic antecedents, noting that a complement of a by-phrase cannot be an antecedent to an NS in Italian, Chinese, Hebrew or Greek. Example (1) shows that in Italian, a by-phrase (da Gianni ‘by John’) in the first clause cannot serve as the antecedent for the NS in the second clause.