David Chalmers argued against the claim that for all p, or even for all entertainable p, it is knowable a priori that p iff actually p. Instead of criticizing Chalmers’s argument, I suggest that it can be generalized, in a sense, and in interesting ways, concerning other principles about contingent a priori truths. In particular, I will argue that the puzzle presented by Chalmers runs parallel to others that do not turn on ‘actually’. Furthermore, stronger arguments can be presented that do not turn on apriority either, though they do entail the conclusion of Chalmers’s argument. All such puzzles involve interactions between rigidifying sentence-forming devices with factive operators.

The issue of‘knowability’ in relation to the origins and distribution ofthe language families of the world is addressed, and recent advances inhistorical linguistics and molecular genetics reviewed. While themuch-debated problem of the validity of the concept of the language‘macrofamily’ cannot yet be resolved, it is argued that a timedepth for the origins of language families greater than the conventionalreceived figure of c. 6000 years may in some cases beappropriate, allowing the possibility of a correlation between languagedispersals and demographic processes following the end of the Pleistoceneperiod. The effects of these processes may still be visible in thelinguistic ‘spread zones’, here seen as often the result offarming dispersals, contrasting with the linguistic ‘mosaiczones’ whose early origins may sometimes go back to initialcolonization episodes during the late Pleistocene period. If further workin historical linguistics as well as in archaeology and molecular geneticsupholds these correlations a ‘new synthesis’, whose outlinesmay already be discerned, is likely to emerge. This would have importantconsequences for prehistoric archaeology, and would be of interest also tohistorical linguists and molecular geneticists. If, however, the proposedrecognition of such patterning proves illusory the prospects for‘knowability’ appear to be lessfavourable.