成唯識論演祕 3.488

3.488

解云：由現作意行相難知故，此舉種以釋體性。雖作是解，其理極難，故今但依第二釋也。謂現作意警覺，現起相應心種，以之為性，現令起種名應起種，非當起種名應起也。

The explanation says: Because the active mode of actual attention is difficult to know, it adduces the seed to explain its essential nature. Although this explanation is offered, its reasoning is extremely difficult, so now one merely relies on the second explanation. That is, actual attention alerts the seed of the associated mind that is actually arising, taking this as its nature; that it presently causes the seed to arise is called 'the seed that ought to arise,' not that a seed due to arise in the future is called 'ought to arise.'