The inclusion of the first criterion means that intentions of this sort go beyond our generic idea of a good intention as simply harmless and well-meaning. Because the roots of skillful intentions are mingled with the roots of unskillful intentions in the soil of the untrained heart.
Skillful roots are mental states in which qualities of greed, aversion, and delusion are absent.
Unskillful roots are states in which these qualities are present. Even when a skillful intention seems foremost in the mind, the unskillful roots can quickly send up shoots that complicate the situation. Of these roots, delusion is the most insidious, for it can blind us to what's going on. When delusion is present, we allow other unskillful roots to develop, mistake unskillful intentions for skillful ones, and misread the results that our intentions produce. For example, we may mistake a mixed intention for a skillful one, and thus get disappointed when it gives mixed results.