The Dayṣanīs were the followers of Bar Dayṣān (in Western sources Bardesanes, d. c.222 C.E.), an Edessene Christian who was deemed heretical within a century of his death. Muslim sources say very little about the Dayṣanīs as a Christian sect and rarely even know that they were Christians. They encountered them mainly as participants in disputations about kalām al-falsafa , natural science pursued in dialectical form, in which the focus was on cosmology as a rational edifice capable of standing alone, without scriptural support. "Dayṣanīs" were those who