This is such a good point. This led me to ponder two points:thereductor wrote: Passaddhi is often rendered as tranquility, as in `it is unmoving` or `still`: like water in an undisturbed glass. In the case of the 7 factors it means the making of the body and mind still, calm, like water in a said glass.
Upekkha is a perceptive mode where an object or event is striped of the normal values of `good` and `bad` (which were based on perceived self interest) and is instead seen in terms of its actual qualities. That is the same meaning it has in relation to the four abodes. We apply the other three mental states fairly to all beings, regardless of how that relates to our own perceived self interest. It can also mean that we ourselves do not go up and down in happiness based on the fortunes of others. Basically it amounts to being imperturbable in the face of any event, but willing to help whenever the opportunity presents itself regardless of the being the is to receive such help.
1. Passaddhi depends on creating stillness, mentally and physically. However, upekkha can happen during mental/physical stillness or in action. In fact, it has to happen while we are active in order to carry it into daily life. We can't stop the world every time we need some equanimity, nor would we want to leave our equanimity on the cushion. "See ya later!"
2. Also, passadhi does not respond to events, it persists despite them (noises, room temperature, etc.) Upekkha can only be in response to events, internal (thoughts, emotions) or external (other peoples' suffering, etc.) If nothing were happening in a given moment, then there would be nothing to maintain equanimity about.