[764] Loving-kindness (mettā) is a root (hetu); the three boundless states (appamaññā) are not roots. [The four boundless states] are accompanied by roots (sahetuka); they are associated with roots (hetusampayutta). Loving-kindness is both a root and accompanied by roots; the three boundless states should not be said to be "both roots and accompanied by roots": they are accompanied by roots but not roots. Loving-kindness is both a root and associated with roots; the three boundless states should not be said to be "both roots and associated with roots": they are associated with roots but not roots. The three boundless states are not roots but accompanied by roots; loving-kindness should not be said to be either "not a root but accompanied by roots" or "not a root and unaccompanied by roots (ahetuka)."
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.