 More recently in a series of papers on Buddhist idealism, Kellner (2017a) revisits Vasubandhu’s argument from ignorance to establish the non-existence of external objects and Dharmakīrti’s objections to it. Dharmakīrti was among the first Indian logician’s to pay attention to how we can know about non-existence. Dharmakīrti is worried about the validity of arguments from ignorance in general and was the first to argue that these arguments cannot be used to establish the absence of a class of entities. He posits non-apprehension (anupalabdhi) as a special kind of reason (hetu) to prove non-existence of objects, but is careful to qualify again that non-apprehension can only prove the situationally specific absence of particular objects, it cannot prove the non-existence of an entire class of objects. Arguments from ignorance and non-apprehension cannot prove the ontological non-existence of objects. Dharmakīrti thus is only interested in supporting the weaker epistemic idealist position that external objects are imperceptible. As far as his arguments go they never establish anything beyond this conclusion. Some, for example Ratié (2014, 361) argue that Dharmakīrti does not need to add anything to this to establish the stronger metaphysical idealism. The stronger thesis follows because of his ontological principle “to be is to be causally efficacious” (arthakriyā). If external objects are completely imperceptible in that they cannt even produce the minimal effect of perceptual awareness, then they are as good as being non-existent. Kellner, however, notes that such a conclusion is excluded by Dharmakīrti’s logical theory which highlights the evidential gap between imperceptibility and non-existence. For him, absence of evidence does not equate to evidence of absence.