Drawing on many areas of expertise, from paleontology to psychology, Tomasello offers a plausible, evolutionary story abouthow our ancestors are likely to have developed cooperative behaviors and collaborative lifeways in order to survive and thrive.He also claims that this narrative explains why they would have begun to think in characteristically cooperative and moral ways,developing a “we is greater than me” [we>me] psychological orientation. Do the arguments offered support this extra claim? Thisarticle suggests that they do not. It seeks to alleviate (...) this shortcoming by drawing upon some conceptual resources offered bySartre’s Theory of Practical Ensembles. The centerpiece of the article consists of a detailed analysis of Sartre’s account of the genesisof the “group-in-fusion,” seeking to show that the genesis of a we-way of thinking in a group made up of many requires themediation of what Sartre calls a “third party” (le tiers). After closely examining Sartre’s treatment of the “third party” in theapocalyptic genesis of the “group-in-fusion,” I evaluate the success of this notion in resolving those questions that Tomasello’saccount raises while, at the same time, addressing the ontological question concerning the nature of the individual-grouprelation, in a way that suggests new and significant alternatives to standard dilemmas in contemporary social philosophy. (shrink)