From Analayo's Satipatthana Sutta Commentary:
http://www.wisdom-books.com/ProductExtr ... ?PID=17023
CHARACTERISTICS AND FUNCTIONS OF SATI
A close examination of the instructions in the Satipatthäna Sutta reveals that the meditator is never instructed to interfere actively with what happens in the mind. If a mental hindrance arises, for example, the task of satipatthana contemplation is to know that the hindrance is present, to know what has led to its arising, and to know what will lead to its disappearance. A more active intervention is no longer the domain of satipatthana, but belongs rather to the province of right effort (samma vayama).
The need to distinguish clearly between a first stage of observation and a second stage of taking action is, according to the Buddha, an essential feature of his way of teaching. The simple reason for this approach is that only the preliminary step of calmly assessing a situation without immediately reacting enables one to undertake the appropriate action.
Thus, although sati furnishes the necessary information for a wise deployment of right effort, and will monitor the countermeasures by noting if these are excessive or deficient, sati nevertheless
Uninvolved and detached receptivity as one of the crucial characteristics of sati forms an important aspect in the teachings of several modern meditation teachers and scholars. They emphasize that the purpose of sati is solely to make things conscious, not to eliminate them. Sati silently observes, like a spectator at a play, without in any way interfering. Some refer to this non-reactive feature of sati as "choiceless" awareness.'" "Choiceless" in the sense that with such awareness one remains impartially aware, without reacting with likes or dislikes. Such silent and non-reactive observation can at times suffice to curb unwholesomeness, so that an application of sati can have quite active consequences. Yet sati's activity is confined to detached observation. That is, sati does not change experience, it deepens it.
This non-interfering quality of sati is required to enable one clearly to observe the building up of reactions and their underlying motives. As soon as one becomes in any way involved in a reaction, the detached observational vantage point is immediately lost. The detached receptivity of sati enables one to step back from the situation at hand and thereby to become an unbiased observer of one's subjective involvement and of the entire situation.' This detached distance allows for a more objective perspective, a characteristic illustrated in the above-mentioned simile of climbing a tower.
This detached but receptive stance of satipatthana constitutes a "middle path", since it avoids the two extremes of suppression and reaction. The receptivity of sati, in the absence of both suppression and reaction, allows personal shortcomings and unjustified reactions to unfold before the watchful stance of the meditator, without being suppressed by the affective investment inherent in one's self-image. Maintaining the presence of sati in this way is closely related to the ability to tolerate a high degree of "cognitive dissonance", since the witnessing of one's own shortcomings ordinarily leads to unconscious attempts at reducing the resulting feeling of discomfort by avoiding or even altering the perceived information.
This shift towards a more objective and uninvolved perspective introduces an important element of sobriety into self-observation. The element of "sobriety" inherent in the presence of sati comes up in an entertaining canonical description of a particular celestial realm, whose divine inhabitants get so "intoxicated" with sensual indulgence that they lose all sati. As a consequence of being without sati, they fall from their elevated celestial position and are reborn in a lower realm.6~ The reverse case is also documented in another discourse, in which negligent monks, reborn in an inferior celestial realm, on regaining their sati are at once able to ascend to a higher realm. Both these instances point to the edifying power of sati and its wholesome repercussions.
Sati as a mental quality is closely related to attention (manasikara), a basic function which, according to the Abhidhaminic analysis, is present in any kind of mental state. This basic faculty of ordinary attention characterizes the initial split seconds of bare cognizing of an object, before one begins to recognize, identify, and conceptualize. Sati can be understood as a further development and temporal extension of this type of attention, thereby adding clarity and depth to the usually much too short fraction of time occupied by bare attention in the perceptual process. The resemblance in function between sati and attention is also reflected in the fact that wise attention (yoniso manasikara) parallels several aspects of satipatthäna contemplation, such as directing attention to antidotes for the hindrances, becoming aware of the impermanent nature of the aggregates or of the sense-pleasures, establishing the awakening factors, and contemplating the four noble truths.
This "bare attention" aspect of sati has an intriguing potential, since it is capable of leading to a "de-automatization" of mental mechanisms. Through bare sati one is able to see things just as they are, unadulterated by habitual reactions and projections. By bringing the perceptual process into the full light of awareness, one becomes conscious of automatic and habitual responses to perceptual data. Full awareness of these automatic responses is the necessary preliminary step to changing detrimental mental habits.
Sati as bare attention is particularly relevant to restraint at the sense doors (indriya sarnvara). In this aspect of the gradual path, the practitioner is encouraged to retain bare sati in regard to all sense-input. Through the simple presence of undisrupted and bare mindfulness, the mind is "restrained" from amplifying and proliferating the received information in various ways. This guardianship role of sati in relation to sense-input is alluded to in those similes that declare satipatthana to be the proper "pasture" for a meditator and which compare sati to the gatekeeper of a town.
According to the discourses, the purpose of restraining the senses is to avoid the arising of desires (abhijjha) and discontent (domanassa). Such freedom from desires and discontent is also an aspect of satipatthana contemplation, mentioned in the "definition" part of the discourse. Thus the absence of reactions under the influence of desires and discontent is a common feature of both satipaffhana and sense-restraint. This goes to show that there is a considerable degree of overlap between these two activities.
To sum up, sati entails an alert but receptive equanimous observation. Viewed from the context of actual practice, a predominantly receptive sati is then enlivened by the quality of being diligent (ätapi), and supported by a foundation in concentration (samadhi).