One thing that should be expressed first and foremost is that the Theravada philosophy is a continuous analytical process of life, not a mere set of ethics and rituals.
The ultimate theory of Theravada uses the Four Noble Truths, also known as the Four Sublime Truths. In the simplest form these can be described as the problem, the cause, the solution and the pathway to solution (implementation).
The Four Noble Truths
A formal description of the Four Noble Truths follows:
1. Dukkha (suffering) - This can be somewhat broadly classified into three categories. Inherent suffering, or the suffering one undergoes in all the worldly activities, what one suffers in day-to-day life: birth, aging, diseases, death, sadness, etc. In short, all that one feels from separating from 'loving' attachments and/or associating with 'hating' attachments is encompassed into the term. The second class of suffering, called Suffering due to Change, implies that things suffer due to attaching themselves to a momentary state which is held to be 'good'; when that state is changed, things are subjected to suffering. The third, termed 'Sankhara Dukkha', is the most subtle. Beings suffer simply by not realizing that they are mere aggregates with no definite, unchanging identity.
2. Dukkha Samudaya (cause of suffering) - Craving, which leads to Attachment and Bondage, is the cause of suffering. Formally, this is termed 'Tanha'. It can be classified into three instinctive drives. 'Kama Tanha' is the Craving for any pleasurable sense object (which involves sight, sound, touch, taste, smell and mental perceptives). 'Bhava Tanha' is the Craving for attachment to an ongoing process, which appears in various forms, including the longing for existence. 'Vibhava Tanha' is the Craving for detachment from a process, which includes non-existence and causes the longing for self-annihilation.
3. Dukkha Nirodha (cessation of suffering) - One cannot possibly adjust the whole world to one's taste in order to eliminate suffering and hope that it will remain so forever. This would violate the chief principle of Change. Instead, one adjusts one's own mind through detachment so that the Change, of whatever nature, has no effect on one's peace of mind. Briefly stated, the third Noble Truth implies that elimination of the cause (craving) eliminates the result (suffering). This is inferred in the scriptural quote by The Buddha, 'Whatever may result from a cause, shall be eliminated by the elimination of the cause'.
4. Dukkha Nirodha Gamini Patipada (pathway to freedom from suffering) - This is the Noble Eightfold Pathway towards freedom or Nirvana. The path can roughly be rendered into English as right view, right intention, right speech, right actions, right livelihood, right effort, right mindfulness and right concentration.
The Three Characteristics
These are the three characteristics of all conditioned phenomena in Theravada thought.
1. Anicca (impermanence): Change is. All conditioned phenomena are subject to Change, including physical characteristics, qualities, assumptions, theories, knowledge, etc. Nothing is permanent, because, for something to be permanent, there has to be an unchanging cause behind it. Since all causes are recursively bound together, there can be no ultimate unchanging cause.
2. Dukkha (suffering) - Craving causes suffering, since what is craved is transitory, changing, and perishing. The craving for impermanent things causes disappointment and sorrow. There is a tendency to label practically everything in the world, as either 'good', 'comfortable' or 'satisfying', as opposed to 'bad', 'uncomfortable', and 'unsatisfying'. Since we label things in terms of 'like' or 'dislike', we create suffering for ourselves. If one succeeds in giving up the tendency to label things and free himself from the instincts that drive him towards attaining what he himself labels collectively as 'liking', he attains the ultimate freedom. The problem, the cause, the solution and the implementation, all of these are within oneself, not outside.
3. Anatta (not-self) - The concept 'Anatta' can be rendered as lack of fixed, unchanging identity; there is no permanent, essential Self. A living being is a composite of the five aggregates (khandhas), which is the physical forms (rupa), feelings or sensations (vedana), perception (sanna), mental formations (sankhara), and consciousness (vinnana), none of which can be identified as one's Self. From the moment of conception, all entities (including all living beings) are subject to a process of continuous change. A practitioner should, on the other hand, develop and refine his or her mind to a state so as to see through this phenomenon.
Direct realization of these three characteristics leads to freedom from worldly bonds and attachments, thus leading to the state where one is completely, ultimately free, the state which is termed Nirvana, which literally means 'Freedom'.
The Three Noble Disciplines
The pathway towards Nirvana, or the Noble Eightfold Pathway is sometimes stated in a more concise manner, known as the Three Noble Disciplines. These are known as discipline (sīla), training of mind (samādhi) and wisdom (paññā).