Jones is known today for his propositions about relationships between the
Indo-European languages. In his
Third Anniversary Discourse to the
Asiatic Society (1786) he suggested that
Sanskrit,
Greek and
Latin languages had a common root, and that indeed they might all be further related, in turn, to
Gothic and the
Celtic languages, as well as to
Persian. Although his name is closely associated with this observation, he was not the first to make it. In the 16th century, European visitors to India became aware of similarities between Indian and European languages and as early as 1653, the Dutch scholar
Marcus Zuerius van Boxhorn had published a proposal for a
proto-language ("Scythian") for
Germanic,
Romance,
Greek,
Baltic,
Slavic,
Celtic and
Iranian. Finally, in a memoir sent to the French Academy of Sciences in 1767
Gaston-Laurent Coeurdoux, a French Jesuit who spent all his life in India, had specifically demonstrated the existing analogy between Sanskrit and European languages. In 1786 Jones postulated a proto-language uniting Sanskrit, Iranian, Greek, Latin, Germanic and Celtic, but in many ways, his work was less accurate than his predecessors, as he erroneously included
Egyptian,
Japanese and
Chinese in the Indo-European languages, while omitting
Hindustani Nevertheless, Jones's third annual discourse before the Asiatic Society on the history and culture of the Hindus (delivered on 2 February 1786 and published in 1788) with the famed "philologer" passage is often cited as the beginning of
comparative linguistics and
Indo-European studies. This common source came to be known as
Proto-Indo-European. Jones was the first to propose the concept of an "
Aryan invasion" into the
Indian subcontinent, which according to Jones led to a lasting ethnic division in India between descents of indigenous Indians and those of the Aryans. This idea fell into obscurity due to a lack of evidence at the time, but was later taken up by amateur Indologists such as the colonial administrator
Herbert Hope Risley. Jones also propounded theories that might appear peculiar today but were less so in his time. For example, he believed that Egyptian priests had migrated and settled down in India in prehistoric times. He also posited that the
Chinese were originally Hindus belonging to the
Kshatriya caste. Jones, in his 1772
Essay on the Arts called Imitative, was one of the first to propound an expressive theory of poetry, valorising expression over description or imitation: "If the arguments, used in this essay, have any weight, it will appear, that the finest parts of poetry, music, and painting, are expressive of the passions...the inferior parts of them are descriptive of natural objects". He thereby anticipated
Wordsworth in grounding poetry on the basis of a Romantic subjectivity. Jones was a contributor to
Hyde's Notebooks during his term on the bench of the Supreme Court of Judicature. The notebooks are a valuable primary source of information for life in late 18th-century Bengal and are the only
extant sources for the proceedings of the
Supreme Court. ==Legal contributions==