 Here are the bare bones of the causal account as we find it in the Pramāṇavārttika: Jones sees particular blue things and they cause perceptual images (ākāra) in his mind; these images (and often other factors, like longstanding habits) cause him to make the “same judgment” (ekapratyavamarśa), “This is blue,” a judgment to which appears an apoha, i.e., a generic representation of non-non-blue. Because the particular perceptual images all have the same effect in leading to the same judgment “This is blue”, they all therefore share a key causal power and are grouped together. The judgments and resulting use of words are about blue things, and not red things, precisely because there is a causal chain from blue particulars and there isn’t one from red  particulars.[42]