After the 1970s Davidson's philosophy of mind picked up influences from the work of Saul Kripke, Hilary Putnam, and Keith Donnellan, all of whom had proposed a number of troubling counterexamples to what can be generally described as descriptivist theories of content. The views, which roughly originate in Bertrand Russell's Theory of Descriptions, held that the referent of a name, which object or person the name refers to, is determined by the beliefs a person holds about that object. Kripke et al. argued that this was not a tenable theory, and that in fact whom or what a person's beliefs were about was in large part (or entirely) a matter of how they had acquired those beliefs, and those names, and how if at all the use of those names could be traced "causally" from their original referents to the current speaker.