According to the excellent, Mindfulness in Plain English, there are three fundamental activities of mindfulness.
We can use these activities as functional definitions of the term: (a) mindfulness reminds us of what we are supposed to be doing, (b) it sees things as they really are, and (c) it sees the true nature of all phenomena.
Here are the three.
1. Mindfulness reminds you of what you are supposed to be doing
In meditation, you put your attention on one item. When your mind wanders from this focus, it is mindfulness that reminds you that your mind is wandering and what you are supposed to be doing. It is mindfulness that brings your mind back to the object of meditation. All of this occurs instantaneously and without internal dialogue. Mindfulness is not thinking. Repeated practice in meditation establishes this function as a mental habit that then carries over into the rest of your life. A serious meditator pays bare attention to occurrences all the time, day in, day out, whether formally sitting in meditation or not. This is a very lofty ideal toward which those who meditate may be working for a period of years or even decades. Our habit of getting stuck in thought is years old, and that habit will hang on in the most tenacious manner. The only way out is to be equally persistent in the cultivation of constant mindfulness. When mindfulness is present, you will notice when you become stuck in your thought patterns. It is that very noticing that allows you to back out of the thought process and free yourself from it. Mindfulness then returns your attention to its proper focus. If you are meditating at that moment, then your focus will be the formal object of meditation. If you are not in formal meditation, it will be just a pure application of bare attention itself, just a pure noticing of whatever comes up without getting involved—“ Ah, this comes up… and now this, and now this… and now this.”
Mindfulness is at one and the same time both bare attention itself and the function of reminding us to pay bare attention if we have ceased to do so. Bare attention is noticing. It reestablishes itself simply by noticing that it has not been present. As soon as you are noticing that you have not been noticing, then by definition you are noticing and then you are back again to paying bare attention.
Mindfulness creates its own distinct feeling in consciousness. It has a flavor— a light, clear, energetic flavor. By comparison, conscious thought is heavy, ponderous, and picky. But here again, these are just words. Your own practice will show you the difference. Then you will probably come up with your own words and the words used here will become superfluous. Remember, practice is the thing.
2. Mindfulness sees things as they really are
Mindfulness adds nothing to perception and it subtracts nothing. It distorts nothing. It is bare attention and just looks at whatever comes up. Conscious thought pastes things over our experience, loads us down with concepts and ideas, immerses us in a churning vortex of plans and worries, fears and fantasies. When mindful, you don’t play that game. You just notice exactly what arises in the mind, then you notice the next thing. “Ah, this… and this… and now this.” It is really very simple.
3. Mindfulness sees the true nature of all phenomena
Mindfulness and only mindfulness can perceive that the three prime characteristics that Buddhism teaches are the deepest truths of existence. In Pali these three are called anicca (impermanence), dukkha (unsatisfactoriness), and anatta (selflessness— the absence of a permanent, unchanging entity that we call Soul or Self). These truths are not presented in Buddhist teaching as dogmas demanding blind faith. Buddhists feel that these truths are universal and self-evident to anyone who cares to investigate in a proper way. Mindfulness is that method of investigation. Mindfulness alone has the power to reveal the deepest level of reality available to human observation. At this level of inspection, one sees the following: (a) all conditioned things are inherently transitory; (b) every worldly thing is, in the end, unsatisfying; and (c) there are really no entities that are unchanging or permanent, only processes.
Mindfulness works like an electron microscope. That is, it operates on so fine a level that one can actually directly perceive those realities that are at best theoretical constructs to the conscious thought process. Mindfulness actually sees the impermanent character of every perception. It sees the transitory and passing nature of everything that is perceived. It also sees the inherently unsatisfactory nature of all conditioned things. It sees that there is no point grabbing onto any of these passing shows; peace and happiness cannot be found that way. And finally, mindfulness sees the inherent selflessness of all phenomena. It sees the way that we have arbitrarily selected a certain bundle of perceptions, chopped them off from the rest of the surging flow of experience, and then conceptualized them as separate, enduring entities. Mindfulness actually sees these things. It does not think about them, it sees them directly.
When it is fully developed, mindfulness sees these three attributes of existence directly, instantaneously, and without the intervening medium of conscious thought. In fact, even the attributes that we just covered are inherently unified. They don’t really exist as separate items. They are purely the result of our struggle to take this fundamentally simple process called mindfulness and express it in the cumbersome and inadequate thought symbols of the conscious level. Mindfulness is a process, but it does not take place in steps. It is a holistic process that occurs as a unit: you notice your own lack of mindfulness; and that noticing itself is a result of mindfulness; and mindfulness is bare attention; and bare attention is noticing things exactly as they are without distortion; and the way they are is impermanent (anicca), unsatisfactory (dukkha), and selfless (anatta). It all takes place in the space of a few mind-moments. This does not mean, however, that you will instantly attain liberation (freedom from all human weaknesses) as a result of your first moment of mindfulness. Learning to integrate this material into your conscious life is quite another process. And learning to prolong this state of mindfulness is still another. They are joyous processes, however, and they are well worth the effort.