to K.L. Dhammajoti, for the Sarvastivada school, 'causal efficacy is the central criterion for the reality/existence (astitva) of a dharma' and hence they were also sometimes called the 'Hetuvada' school. A dharma is real because it is a cause and it has effects, if it had no causal efficacy, it would not exist. The six causes outlined by the Sarvastivada are: Efficient cause (karana-hetu) – dharma A, causes dharma B Homogeneous cause (sabhäga-hetu) – dharma A(1) causes another dharma A(2) Universal cause (sarvatraga-hetu) – a Homogeneus cause, pertaining only to defiled dharmas Retribution cause (vipäka-hetu) – leads to karmic retribution Co-existent cause (sahabhu-hetu) – a cause which arises from the mutuality of all dharmas, a 'simultaneous causality.' Conjoined cause (samprayuktaka-hetu) In the Mahavibhasa treatment of dependent origination, four different types are outlined: Momentary (ksanika) causation, as when all twelve moments of the chain are realized in a single moment of action Serial (sambandhika) causation, in which dependent origination is viewed in reference to the relationship between cause and effect Static (avasthika) causation, in which dependent origination involves twelve distinct periods of the five aggregates Prolonged (prakarsika) causation, in which that sequence of causation occurs over three lifetimes The Sarvastivada Vibhasa-sastrins accepted only static dependent origination The last book of the Pali Abhidhamma, the Patthana, sets out the main Theravada theory on conditioned relations and causality. The Patthana is an exhaustive examination of the conditioned nature (Paticcasamupada) of all dhammas. The introduction begins with a detailed list of 24 specific types of conditioned relationships (paccaya) that may pertain between different factors. The majority of these conditions have counterparts in the Sarvāstivāda Abhidharma. The Pali Abhidhammatthasangaha reduces them all to four main types. The Sautrāntika school used a theory of 'seeds' (bīja) in the mental continuum to explain causal interaction between past and present dharmas, this theory was later developed by the Yogacara school in their theory of “storehouse consciousness” (ālayavijñāna). Temporality A prominent argument between the Abhidharmikas was on the Philosophy of time. The Sarvāstivādin tradition held the view (expressed in the Vijñanakaya) that dharmas exist in all three times – past, present, future; hence the name of their school means "theory of all exists". The Sautrāntika, Vibhajyavāda and Theravada schools argued against this eternalist view in favor of presentism (only the present moment exists). This argument was so central, that north Indian Buddhist schools were often named according to their