The Buddha was the foremost scientist of mind and matter (nama and rupa). What makes him a peerless scientist is his discovery that tanha, or craving, and by extension, aversion—arises from vedana, or sensation on the body.

Before the time of the Buddha, little if any importance was given to bodily sensation. In fact, it was the centrality of bodily sensation that was the Buddha’s great discovery in his quest to determine the root cause of suffering and the means to its cessation. Before the Buddha, India’s spiritual masters emphasized teachings that encouraged people to turn away from sensory objects and ignore the sensations that contact with them engenders.

But the Buddha, a real scientist, examined sensation more closely. He discovered that when we come into contact with a sense-object through one of the six sense doors (ears, eyes, nose, tongue, body, mind), we cling to the sensation it creates, giving rise to tanha (wanting it to stay and to increase) and aversion (wanting it to cease). The mind then reacts with thoughts of either “I want” or “I do not want.” Buddha discovered that everything that arises in the mind arises with the sensations on the body and that these sensations are the material we have to work with.

The first step, then, is to train the mind to become so sharp and sensitive that it will learn to detect even the subtlest sensations. That job is done by anapana—the practice of awareness of the breath—on the small area under the nostrils, above the upper lip. If we concentrate on this area, the mind becomes sharper and sharper, subtler and subtler. This is the way we begin to become aware of every sort of sensation on the body.

Next, we feel the sensations but don’t react to them. We can learn to maintain this equanimity towards sensations by understanding their transitory nature.

Whether pleasant, unpleasant, or neutral, gross or subtle, every sensation shares the same characteristic: it arises and passes away, arises and passes away. It is this arising and passing that we have to experience through practice, not just accept as truth because Buddha said so, not just accept because intellectually it seems logical enough to us. We must experience sensation’s nature, understand its flux, and learn not to react to it.

As we reach deeper states of awareness, we will be able to detect subtler and subtler sensations, or vibrations of greater rapidity, arising and passing with greater speed. In these deep states, our mind will become so calm, so tranquil, so pure, that we will immediately recognize any impurity accompanying the agitated state and make the choice to refrain from reacting adversely. It becomes clear to us that we can’t harm anybody without first defiling ourselves with emotions like hate or anger or lust. If we do this, we will come to an experiential understanding of the deep truth of anicca, or impermanence. As we observe sensations without reacting to them, the impurities in our minds lose their strength and cannot overpower us.

The Buddha was not merely giving sermons; he was offering a technique to help people reach a state in which they could feel the harm they do to themselves. Once we see this, sila, or ethics, follows naturally. Just as we pull our hand from a flame, we step back from harming ourselves and others.

It is a wonderful discovery that by observing physical sensations on the body, we can eradicate the roots of the defilements of mind. As we practice more, negative emotions will become far more conspicuous to us much earlier; as soon as they arise, we will become aware of sensations and have the opportunity to make ethical choices. But first we need to begin with what is present to us deeply in our minds at the level of sensation. Otherwise, we will keep ourselves and others miserable for a very long time.