Dead and dying duals meet the Agreement Hierarchy: Upper Sorbian clarifies the nature of ‘semantic agreement’

The dual in Colloquial Upper Sorbian is in severe decline. It is now largely limited to use with dwaj/dwě ‘two’ and wóbej/wóboj ‘both’. Dual agreement is being replaced by plural agreement, with dual agreement now restricted mainly to attributive position. We document this interesting situation from a range of sources, and give native speaker judgements on the alternative agreements. It has been claimed that the development is in accord with the Agreement Hierarchy, and indeed the monotonic pattern of agreement alternatives fits the constraint of the Hierarchy. However, it is not self-evident which value of the number feature (dual or plural) should count as semantic agreement. Recent work on the Agreement Hierarchy shows that, rather than looking at feature values (the symptoms), we need to appeal to the competing sources of agreement. To do this, a Hierarchy of Agreement Sources has been proposed, orthogonal to the Agreement Hierarchy, and this specifies which agreement alternative will count as showing generalized semantic agreement. We demonstrate that the data from Colloquial Upper Sorbian can be analysed in this way, thus adducing novel data to support our much more general typological claim.