The controversial hypotheses in question fall into two categories. Some of them involve the application of standard historical linguistic methodology in ways that raise doubts as to the validity of the hypothesis. A good example of this sort is the Moscow school of Nostraticists, founded by
Vladislav Illich-Svitych and including
Aharon Dolgopolsky,
Sergei Starostin, and
Vitaly Shevoroshkin, who have argued for the existence of
Nostratic, a language
macrofamily including the
Indo-European,
Afro-Asiatic,
Altaic,
Dravidian, and
Kartvelian language families and sometimes other languages. They have established regular phonological correspondences, observed morphological similarities, and reconstructed a proto-language in accordance with the accepted methodology. Nostratic is not generally accepted, in part because critics have doubts about the accuracy of the correspondences and reconstruction. Other hypotheses are controversial because the methods used to support them are considered by mainstream historical linguists to be invalid in principle. Into that category fall proposals based on
mass comparison, a technique in which relationships are postulated on basis of sets of words resembling each other in sound and meaning, without establishing phonological correspondences or carrying out a reconstruction. Prominent examples are the work of
Joseph Greenberg and
Merritt Ruhlen. Most linguists reject that method as unable to distinguish similarities from common ancestry from those from
borrowing or chance. ==See also==