成唯識論述記 5.340

5.340

述曰：何意有定？專注一類所執我境，不暫捨故。如於志念緣曾受境，此緣一物，故有定也。不同前師，彼無念故，緣新新現境故亦無定，此中有之所存別故。

The Commentary states: For what reason is concentration present? Because it focuses exclusively on a uniform apprehended self-object without relinquishing it for an instant. Just as with intention and mindfulness taking a previously experienced object as their object, this takes a single thing as its object; therefore concentration is present. This is not like the previous master: because he posited no mindfulness, taking ever-new present objects, there was also no concentration; here it is present because what is posited is different.