Nyāya Sūtras 78

And the designations 'means of valid cognition' and 'object of valid cognition' apply concurrently due to the occasion for the designation. The occasion for the designation, however, is that the means of apprehension is the means of valid cognition, and the object of apprehension is the object of valid cognition. And when the object of apprehension is somewhere the means of apprehension, then one and the same entity is referred to as 'means of valid cognition' and 'object of valid cognition'. To illuminate this point, this is said:

And [the means of valid cognition] is also an object of valid cognition, like the validity of a balance.

A balance, being the means of knowing the measure of weight, is a means of valid cognition; the heavy substance that is the object of knowledge, such as gold, is an object of valid cognition. When another balance is adjusted by means of the gold or the like, then, in the apprehension of the other balance, the gold or the like is the means of valid cognition, and the other balance is the object of valid cognition. In this way, the meaning of the treatise is to be understood as indicated without remainder. The self, first of all, is enumerated among objects of valid cognition because it is an object of apprehension; it is the cognizer because of its independence in apprehension. Cognition is a means of valid cognition because it is a means of apprehension; it is an object of valid cognition because it is an object of apprehension; but in the absence of both, it is valid cognition. Thus the concurrence of designations should be applied to specific entities. And in this manner, words expressing grammatical roles apply concurrently depending on the occasion.

In 'the tree stands', [the tree] is the agent because of its independence in its own staying. In 'he sees the tree', it is the direct object because it is what is most desired to be reached by seeing.

In 'he makes known the moon by means of the tree', it is the instrument because it is the most effective means for the one who makes it known.

In 'he pours water for the tree', it is the recipient because he intends the tree by means of the water being poured. In 'a leaf falls from the tree', it is the point of departure according to 'that which is fixed in moving away is the point of departure'. In 'birds are in the tree', it is the locus according to 'the substrate is the locus'. And this being so, a mere substance is not a grammatical role, nor is a mere action. What then? A means of action endowed with a specific action is a grammatical role. That means of action which is independent is the agent, not a mere substance, not a mere action. What is most desired to be reached by an action is the direct object,

not a mere substance, not a mere action. So too in the case of the most effective means and the rest. And thus the grammatical explanation of grammatical roles is just as it is from reasoning, so it is from definition. The grammatical explanation of grammatical roles is also not in reference to a mere substance, nor to an action. What then? In reference to a means of action endowed with a specific action. And this word for a grammatical role is 'means of valid cognition' and 'object of valid cognition'; and it cannot abandon the nature of a grammatical role.