In other words, once more Vasubandhu is making a point about praxis, explaining that through recognizing dharmas for what they are, that is, by understanding phenomena to be "perception-only", we are able to realize their emptiness, or, to use his word, their "selflessness".
Put this way, the issue of whether or not external objects exist is completely avoided and in fact, Vasubandhu is actually warning us against taking this approach. This, therefore, coheres with the interpretation given above according to which for the Yogācāra, as for the Madhyamaka, the highest reality is inexpressible, and the
enlightened being avoids making claims about existence and nonexistence. The doctrine
of "mind-only", or better, "perception-only", on this account, is merely a provisional
construct intended as an aid to realizing emptiness.
In a further text, Vasubandhu specifies that one must experience the emptiness of "perception-only" too (TK 25–27;Anacker 2005, 189).
(((Anacker translates the passage as follows:
As long as consciousness is not situated within perception-only
The residues of a "dual" apprehension will not come to an end.
And so even with the consciousness: "All this is perception only",
Because this also involves an apprehension,
For whatever makes something stop in front of it isn‘t situated in "this-only" (2005, 188–189).)))
Vasubandhu explains, in these verses, that to grasp at the idea that "all this is
perception-only",(and, one might add here, that this true of most idealists) involves a
dualism; on the one hand, there is the object, perception-only, which one claims to
perceive, and on the other, there is a subject who perceives the object. Thus, the idea is dissolved, as it is seen to involve another perception, and to be, consequently,
"perception-only" (TK 27).
The relation between this verse, and Nāgārjuna‘s doctrine on the emptiness of emptiness should be clear; both consist of a warning not to remain attached to any Buddhist doctrine, and a reminder that each one needs to be discarded along the way.