doctrine of the existence of external things, viz. 'the
perception of external things is admitted to take place also without
mental impressions,' and 'mental impressions are not admitted to
originate independently of the perception of external
things.'--Moreover, an impression is a kind of modification, and
modifications cannot, as experience teaches, take place unless there is
some substratum which is modified. But, according to your doctrine, such
a substratum of impressions does not exist, since you say that it cannot
be cognised through any means of knowledge.

31. And on account of the momentariness (of the alayavij/n/ana, it
cannot be the abode of mental impressions).

If you maintain that the so-called internal cognition
(alayavij/n/ana[410]) assumed by you may constitute the abode of the
mental impressions, we deny that, because that cognition also being
admittedly momentary, and hence non-permanent, cannot be the abode of
impressions any more than the quasi-external cognitions
(prav/ri/ttivij/n/ana). For unless there exists one continuous principle
equally connected with the past, the present, and the future[411], or an
absolutely unchangeable (Self) which cognises everything, we are unable
to account for remembrance, recognition, and so on, which are subject to
mental impressions dependent on place, time, and cause. If, on the other
hand, you declare your alayavij/n/ana to be something permanent, you
thereby abandon your tenet of the alayavij/n/ana as well as everything
else being momentary.--Or (to explain the Sutra in a different way) as
the tenet of general momentariness is characteristic of the systems of
the idealistic as well as the realistic Bauddhas, we may bring forward
against the doctrines of the former all those arguments dependent on the
principle of general momentariness which we have above urged against the
latter.

We have thus refuted both nihilistic doctrines, viz. the doctrine which
maintains the (momentary) reality of the external world, and the
doctrine which asserts that ideas only exist. The third variety of
Bauddha doctrine, viz. that everything is empty (i.e. that absolutely
nothing exists), is contradicted by all means of right knowledge, and
therefore requires no special refutation. For this apparent world, whose
existence is guaranteed by all the means of knowledge, cannot be denied,
unless some one should find out some new truth (based on which he could
impugn its existence)--f