In social research, causal explanations have generally been implemented through the lens of methodological and ontological individualism. In this chapter we present the details of the arguments that have been developed by emphasizing how methodological individualists make sense of mechanism-based explanations through the use of micro-foundations. We bring to light the reductionistic character of these explanations because they identify mechanisms either with the rationality of the actors or with the situational demands they face. In contrast to these cases of reductionism, we provide arguments that prioritize the irreducibility of the social through the philosophical concept of wild disjunction. Furthermore, we show why singular causation fits perfectly with biographical research because of the role context and relational properties play in shaping life experiences.