Dignāga on the Causality of Object-Support (Ālambana) and Śubhagupta's Refutation

To answer the question about an internal object serving as a cause of cognition, in his Ālambanaparīkṣāvṛtti, Dignāga elaborates two types of causality in the significance of object-support (ālambana): simultaneous causality and successive causality. Simultaneous causality is characterized as invariably concomitant (avyabhicārin), which refers to the inevitable co-existence of an object and its cognition. Successive causality is characterized as resemblance (anurūpa), which refers to a definite causal relationship between the immediate previous consciousness and its subsequent consciousness. That is, the preceding consciousness remains a potential power that transmits gradually to the subsequent consciousness. The potential power is carried with an object appearance in the stream of consciousness and becomes an actual internal object similar to the previous object in the subsequent consciousness. There are two alternatives of Dignāga's ambiguous interpretation: either the internal object of the previous consciousness or the potential power can be regarded as an object-support for the subsequent consciousness. However, in his Bāhyārthasiddhikārikā, Śubhagupta criticizes both alternatives, writing that neither of these two serves as an object-support because neither appears in the subsequent consciousness. Therefore, they fail to fulfil the first requirement of an object-support even though they could fulfil the second requirement of an object-support. In addition, Śubhagupta argues that the causal relationship between the preceding consciousness and its subsequent consciousness is not necessary.