Bartholomae's law
Bartholomae's law, sometimes referred to as the Buddha rule, is a Proto-Indo-European sound law affecting consonant clusters, most clearly in the Indo-Iranian languages. It states that in a cluster of two or more obstruents, any one of which is a voiced aspirated stop anywhere in the sequence, the whole cluster becomes voiced and aspirated. Thus, to the Proto-Indo-European root bʰewdʰ- 'learn, become aware of', the participle bʰudʰ-to- 'enlightened' loses the aspiration of the first stop and with the application of Bartholomae's law and regular vowel changes gives Sanskrit 'enlightened'. The law is named after German linguist Christian Bartholomae, who first described it in 1883.
Further developments
In both the Indic and the Iranian subgroups, further developments partially obscured the operation of the law; thanks to the falling together of plain voiced and voiced aspirated stops in Iranian, Bartholomae's law appears synchronically as progressive voicing assimilation after roots that originally ended in voiced aspirates, for example Old Avestan italic=unset 'he said' from Proto-Indo-European Hewgʰ-to-. This is not true for roots with plain voiced stops, for example Old Avestan 'yoked' from Proto-Indo-European yug-to-, where Bartholomae's law does not apply.In Indic, voiced *z as resulting from Bartholomae's law was devoiced to s, although there is some evidence from the Rigvedic language that a voiced aspirate *z once existed in Indic as well. This is shown by forms like gdha 'he swallowed' and dudukṣa- 'want to give milk'.
Interpretation
A written form such as -ddh- presents problems of interpretation. The choice is between a long voiced stop with a specific release feature, aspiration, symbolized in transliteration by -h-, or else a long stop with a different phonational state, "murmur", whereby the breathy release is an artifact of the phonational state. The latter interpretation is rather favored by such phenomena as the Rigvedic form gdha 'he swallowed', which is morphologically a middle aorist to the root ghas- 'swallow', as follows: ghs-t-a > *gzdha, whence gdha by the regular loss of a sibilant between stops in Indic. While the idea of voicing affecting the whole cluster with the release feature conventionally called aspiration penetrating all the way to the end of the sequence is not entirely unthinkable, the alternative – the spread of a phonational state through the whole sequence – involves one less step and therefore via Occam's razor counts as the better interpretation.Bartholomae's law intersects with another Indic development, namely what looks like the deaspiration of aspirated stops in clusters with s: descriptively, Proto-Indo-European leyǵʰ-si 'you lick' becomes *leyksi, whence Sanskrit. However, Grassmann's law, whereby an aspirated stop becomes non-aspirated before another aspirated stop, suggests something else. In late Vedic and later forms of Sanskrit, all forms behave as though aspiration was simply lost in clusters with s, so such forms to the root dugh- 'give milk' show the expected devoicing and deaspiration in, say, the desiderative formation du-dhukṣ-ati. But the earliest passages of the Rigveda show something different: desiderative dudukṣati, aorist dukṣata and so on. Thus, it is apparent that what went into Grassmann's law were forms like *dhugzhata, dhudhugzha- and so on, with aspiration in the sibilant clusters intact. The deaspiration and devoicing of the sibilant clusters were later and entirely separate phenomena. Even the example 'swallowed' given above contradicts the usual interpretation of devoicing and deaspiration: by such a sequence, *ghs-to gave, first, *ksto or *ksta, whence Sanskrit *kta, not gdha.