comparative method syntax fritz newmeyer ask legitimate apply comparative method syntax answer ye difficult main reason why one work historicalcomparative syntax fifty ago syntax become much prestigious recent decade nt shift once standard view syntactic reconstruction impossible bernhard delbrueck s historicalcomparative syntax indo european publish hundr ago clearly show comparative syntax both possible fruitful perhap too difficult attract many follower view historicalcomparative syntax impossible defend detail lightfoot s principle diachronic syntax few researcher seem discourage lightfoot s attitude true latin syntax hardly reconstruct modern romance language neither latin morphology even view latin phonology romance distort our reconstruction protolanguage grammar alway imperfect reason attempt reconstruction main error lightfoot s side syntactic analog regularity sound change s bite complicate syntax syntax complicate overall phonology basically analog phoneme word word sentence true difference between word sentence general sentence store lexicon neither many complex word render morphological reconstruction similarly difficult nobody seem ever object morphological reconstruction sentence actually store e g proverb idiom often show syntactic archaism since earlier syntax often survive fossilize form later morphology another rich source datum diachronic syntax addition regularity change need general principle change plausible reconstruction e g phonological principle predict likely change assimilation lenition segment loss etc syntax similar principle change exist spatial noun become spatial adposition certain general verb become tense aspect marker allative case marker become dative case marker purposive verb form become infinitive etc process instance grammaticalization irreversible change provide safe guide linguist seek sense daughter language diversity reconstruct protosyntax massive regularity grammaticalization generally ignore generative study syntactic change indeed lightfoot argue genuine principle diachronic syntax one account help difficult task reconstruction martin haspelmath free university berlin 