Gergen, K. (1998) Constructionism and realism: how are we to go on? In I. Parker (ed) "Social constructionism, discourse and realism." London:Sage. 
(click here for paraphrase.)

In this very recent paper, Gergen talks about the importance of both realism and constructionism as resources: 

Are these explicit references to realism something new in Gergen's work? I haven't found anything like it in the Saturated Self or articles I have read. 

Regarding the concept of realism, I like the idea of a continuum between a naive realism and a mediated realism because I have begun to doubt that realism and constructionism must be the kind of stark binary that we are more familiar with.  On the one end are  those who believe we can see the world directly without any intervening distorting perceptual processes (naive realists - or those who would hold a reflection correspondence theory of truth) and on the other are those who feel that we can know reality a little better through our constructions but recognise that such constructions are always provisional and challengeable. Some realists seem also to recognise the distorting and enchanting properties of language. 

I would argue that Anderson, Goolishian and then later Hoffman who they strongly influenced brought into family therapy an extreme relativist version of social constructionism. (For example, A and G in their very influential 1988 paper say explicitly that they do not believe there are any "real external entities" beyond conversation.)