Four foundations as sequential observation fields
Mindfulness is established in four domains: body (breath, posture, activity, anatomical parts, elements, corpse decay), feelings (pleasant, unpleasant, neutral), mind states (with or without lust, hatred, delusion), and mental phenomena (hindrances, aggregates, sense bases, awakening factors, Four Noble Truths). Each domain is observed 'internally, externally, and both,' noting both its arising and its passing away. The practitioner abides 'independent, not clinging to anything in the world,' and the aim is to see that every domain is a stream of events with no owner behind it.