Dr Israel Isidor Elyashev (1873–1924) was a Jewish neurologist and literary critic.

Elyashev's pen name was “Ba'al Machshavot” (Yiddish for “The Thinker”. He was trained as a physician, specialising in neurology, but is best known for his work as a literary critic, writing in Yiddish. He translated Theodore Herzel 's Altneuland from German into Yiddish. His attitude to Jewish literature and the two great Jewish languages, Yiddish and Hebrew is summed up by something that he wrote in 1918:

[W]e have two languages and a dozen echoes from other foreign languages, but ... we have only one literature. And therefore the reader who seeks to become acquainted with the currents of Jewish life, to comprehend the spirit of the Jewish individual and multitude and how they find expression in Jewish literature, that reader does not separate Hebrew writers from Yiddish ones. ...All are representatives of our literature, all embody a piece of Jewish life in their writings; all of them are Jewish artists. [1]

Elyashev was also politically active, being involved with a forerunner of the Zionist Movement, and was a delegate from Germany to the First Zionist Congress in Basel, Switzerland in August 1897 .