Both you and cperciva seem to be fundamentally theory people. IMO, you both completely missed what mencius meant when he wrote 'soundest.' When he says sound, he means that a field is worthwhile, both because it has problems that are interesting in a purely technical way and because solutions to them are in some way actually useful to non-CS humanity. When you say sound, you mean pedantically verifiable for the benefit of other theorists. Graphics is sound because not only does it have interesting math, it aids or entertains laymen; PL research isn't, because nobody except PL researchers cares.