Just like the case of those with cataracts seeing unreal hairs in the moon and the like."According to Vasubandhu then, all our experiences are like seeing hairs on the moon when we have cataracts, that is, we project our mental images into something "out there" when there are no such things. Vasubandhu then goes on to use the dream argument to argue that mental impressions do not require external objects to (1) seem to be spatio-temporally located, (2) to seem to have an inter-subjective quality, and (3) to seem to operate by causal laws. The fact that purely mental events can have causal efficacy and be intersubjective is proved by the event of a wet dream and by the mass or shared hallucinations created by the karma of certain types of beings.