The Romance languages possess several mechanisms to express different types of speaker attitude towards the content of a clause: adverbs like probablement 'probably' and verbal forms like the conditional can be used to express the degree of certainty that a speaker has over the content of a clause (a notion often labelled as epistemicity) and whether they got that information first hand, the information is common knowledge or something they've been told by someone else (a concept referred to as evidentiality). In addition, another strategy is available for the expression of epistemicity and evidentiality: constructions where we find an element with epistemic or evidential semantics followed by a sentence headed by que:
Segur que demà plou.
sure that tomorrow will.rain
'I am sure that tomorrow will rain'.
Evidentment que demà plourà.
evidently that tomorrow will.rain
'It is evident (to me) that tomorrow will rain'.
In recent research, I have explored how these structures came to be in Old Catalan and what they can tell us about the sentential structure of the language at different points in time.
I have also looked into the use and syntactic structure of different particles linked to the expression of positive and negative polarity (as well as speaker attitude) shared by Catalan and Occitan: bé/be, ben and pla/plan. The comparison of the use and distribution of these particles in different Catalan and Occitan varieties can inform us about the common past of these languages and how they differ syntactically from other Romance varieties. See Pujol i Campeny (forthcoming) for more on the matter.
I am currently developing other ideas connected to this line of research, also touching upon other Romance varieties from the Pyrenaic linguistic continuum.