瑜伽師地論略纂 2.22

2.22

The four powers of attentiveness: The first three kinds take future, past, and present objects as their spheres, in respective order; the fourth single power takes the three times universally as its sphere. "If it were other than this, attentiveness would arise exclusively toward a single intentional object at all times": If it were different from the previously explained arising of attentiveness through the four powers, one attentiveness would constantly arise toward a single object. Therefore, we know it must depend upon the four powers.