The Perfection of Energy - Different aspects and degrees of viriya

When viriya has been further developed, additional aspects and degrees can be discerned, for instance: viriya as a predominant factor (adhipati), as a basis of success (iddhi-pada), as a faculty (indriya) or a power (bala).
When viriya has not reached those degrees, one cannot understand the  characteristic of viriya that accompanies satipatthana and that has become strong.
As we have seen, viriya has been classified among the faculties, indriyas (leaders each in their own field). These are:

the faculty of confidence, saddha,

the faculty of sati,

the faculty of panna,

the faculty of energy, viriya,

the faculty of concentration, samadhi.

  These faculties arise together and thus, the faculty of viriya which arises together with confidence, sati, panna and samadhi must be kusala viriya.
Realities can be classified in different ways, for example, by way of the four bases of success, iddhi-pada (leading to enlightenment):

wish-to-do (chanda)

energy (viriya)

citta (firmness of citta or concentration)

investigation (vímansa).
Thus we see that there are different aspects of viriya. The cetasikas which are faculties are not identical with the cetasikas which are bases of success. Such classifications are very detailed, but they show us that kusala viriya is of different degrees.