Topic XP-nun and intervention effects

This　squib explores the behavior of so called contrastive topic phrases (i.e. XP-nun phrases) in relation to other A'-phrases. XP-nun phrases exhibit dual nature in that they sometimes induce intervention effects but not in other cases. The usual assumption that the contrastive topic phrases are　licensed by a higher head Top is questioned in this paper because it doesn't provide any account for this asymmetry in intervention effects. Instead an alternative proposal is considered such that XP-nun is not the target of licensing but forms a kind of self saturated domain in which both the licenser (=nun) and the licensee (=a focus target within XP) are contained. It is shown that this proposal can not only account for the asymmetry in the intervention effects, but can accommodate unexpected saving effects in some focus constructions.