In a conversation with an aged brahmin, the Buddha once explained concisely what is meant by a Buddha, an enlightened one:

“What has to be known, that I have known;
What has to be abandoned, that I have abandoned;
What has to be developed, that I have developed;
Therefore, O brahmin, I am a Buddha.”

These are not only three characteristics of a Buddha; they are also the three objectives we aim at in following the Buddha’s teaching. We follow the Dhamma to fully know what should be known; to abandon what should be abandoned; and to develop what should be developed. These are the goals of the Buddhist path and the three accomplishments that mark the attainment of enlightenment.

What does it mean to say that our task is “to know that which should be known”? What we have to know, what we have to understand, is that which is closest to ourselves, what we usually refer to as our self. What we usually refer to as our self is this complex of body and mind. For most of us, from the time we are born right up to the time of our death, our minds are oriented outwardly, engaged in a tireless quest for pleasure and sensual gratification, for the enhancement of our self, for the confirmation of our sense of ego-identity. Very few people stop and turn around to consider the question, “What is it that I call my self? What is it that I refer to as my self?” And yet, if you reflect for just a moment, you will see that this is the most important question we can ask.

So our task in following the Buddha’s teaching is to investigate, to examine, that which we refer to as “I,” as “my self,” as “what I am.” We usually take these terms to refer to some kind of persisting entity, an ego, a substantial self possessing a real identity, but what the Buddha asks us to do is to see what we find when we look for the referents of the terms, “I,” “me,” and “my self.” When we look, when we investigate, what we find are just components of bodily and mental experience, which the Buddha has classified into five aggregates: physical form, feeling, perception, volitional formations, and consciousness. These are called the “five aggregates of clinging” because they are the things that we ordinarily cling to as, “This is mine, this is what I am, this is my true self.” Our task in following the Buddha’s teaching is to understand the true nature of these five aggregates. We thereby come to know that which constitutes our identity. From birth, through adulthood, through old age, to death — this whole process of life is just a procession of the five aggregates.

The second project the Buddha’s teaching sets for us is “to abandon that which should be abandoned.” What should be abandoned are the defilements. The Buddha uses the word kilesas as an umbrella term that includes all the mental states that cause suffering and unhappiness in our lives. The unwholesome mental states are called kilesas. The word can be translated afflictions because they bring suffering. It can also be translated defilements because they defile and corrupt the mind. The Buddha has analyzed the nature of the defilements and has beautifully explained how they can all be traced to the three “root defilements” of greed, hatred, and delusion. Our task in following the Buddha’s teaching, in practicing the Dhamma, is to overcome, to eliminate, to abandon the defilements of greed and hatred that give rise to many other branch defilements. But greed and hatred spring ultimately from delusion or ignorance. And thus to eliminate all the defilements, we have to eliminate ignorance.

Ignorance is what covers up the five aggregates, that which should be known. Thus the way to overcome ignorance is through the first task — “knowing that which should be known.” When we know that which should be known, ignorance falls away — and then greed, hatred, and all the other defilements fall away. It isn’t possible, however, to accomplish this merely by having the desire to do so. We can’t expect simply to think, “I want to know that which should be known,” and immediately it is known. That’s why the whole practice of Buddhism is a process of walking a path. The great gift that the Buddha offers the world is not simply a profound philosophy, not simply a very penetrating psychology, but a practical, systematic, step-by-step path that we can cultivate in sequence.

To cultivate the path means to “develop that which should be developed.” That is the third project the Buddha speaks of in his four-line verse: “That which should be developed, that I have developed.” So what the Buddha has developed is what we have to develop. The path is structured in such a way that it proceeds not suddenly, not abruptly, but in a gradual step-by-step manner to help us climb the ladder to the ultimate freedom of enlightenment. One has to begin by keeping the coarser expression of the defilements under control. One does this by observing the precepts, the Five Precepts or the Eight Precepts. These control the coarser expressions of the defilements, the way the defilements break out or erupt in the form of unwholesome actions.

We next have to cultivate concentration. When we try to collect the mind, we gain insight into the workings of our own minds. By understanding the workings of our own minds, we’re gradually changing the shape of the mind. First, we are beginning to scrape away the soil in which the unwholesome roots have been lodged. The process isn’t a quick or easy one, but requires gradual, persistent, and dedicated effort. As one practices consistently, the mind will eventually settle into firm concentration. It acquires the skills needed to remain consistently settled upon an object, without wavering, and this provides the opportunity for wisdom to arise.

Wisdom is the third quality that needs to be developed. Wisdom comes through examination, through investigation. When one has developed a strongly concentrated mind, one uses that mind to investigate the five aggregates. As one investigates, one directly sees into their real nature, into “the true characteristics of phenomena.” Generally, one first sees the arising and falling away of the five aggregates. That is, one sees their impermanence. One sees that because they’re impermanent, they’re unsatisfactory. There’s nothing worth clinging to in them. And because they’re impermanent and unsatisfactory, one cannot identify with any of them as a truly existing self. This is the empty or self-less nature of the five aggregates. This marks the arising of true insight wisdom.

With insight-wisdom, one cuts deeper and deeper into the root of ignorance until one comes to fully understand the nature of the five aggregates. When one does so, one can then say that one has “known that which should be known.” And by fully knowing that which should be known, the defilements “that should be abandoned have been abandoned,” and the path “that should be developed has been developed.” One then realizes that which should be realized, the extinction of suffering right here and now. And, in the Buddha’s own words, that is the mark of an Enlightened One.