The notions of selflessness (anātmaka) and karman are two key concepts in Buddhist philosophy. The question how karman functions with respect to the rebirth of a worldling who is, actually, devoid of a self, was a major philosophical issue in early Buddhist doctrine. Within the Sarvāstivāda school, the Vaibhāsikas became the representative of an interpretation of this problem that hinges on the notion of 'possession' (prāpti). Their theory was contradicted by the Sautrāntikas, whose interpretation is based on the notion of 'seed' (bija). The Sarvāstivāda Hr˙daya treatises, compiled in a time period spanning from the beginning of the common era to the fourth century AD, i.e. the period of the rise of the Sautrāntika school, are a particularly interesting set of works, as they reflect the gradual development of these two major theories.