Sefer HaYashar - The Book of Righteousness

Sefer Ha-Yashar [The Book of Righteousness]. One of the most popular ethical books in the Middle Ages. It was attributed to Rabinu Tam, the Tosafist. The style and language conform to contemporaneous philosophical and ethical writings and ideas; the author specially made use of Aristotelian terms and concepts. He includes several other beliefs which hint at possible Qabbalistic tendencies. The work is also similar in substance to ideas present amongst Hasidei Ashkenaz.