Buddhist philosophy deals extensively with problems in metaphysics, phenomenology, ethics, and epistemology.
Some scholars assert that early Buddhist philosophy did not engage in ontological or metaphysical speculation, but was based instead on empirical evidence gained by the sense organs (ayatana). Buddha is said to have assumed an unsympathetic attitude toward speculative thought in general. A basic idea of the Buddha is that the world must be thought of in procedural terms, not in terms of things or substances. The Buddha advised viewing reality as consisting of dependently originated phenomena; Buddhists view this approach to experience as avoiding the two extremes of reification and nihilism. Nevertheless, Buddhist scholars have addressed ontological and metaphysical issues subsequently.
Particular points of Buddhist philosophy have often been the subject of disputes between different schools of Buddhism. While theory for its own sake is not valued in Buddhism, theory pursued in the interest of enlightenment is consistent with Buddhist values and ethics.
Early Buddhism displays a strong streak of skepticism; the Buddha cautioned his followers to stay aloof from intellectual disputation for its own sake, saying that this is fruitless and distracts from the practices leading to enlightenment. However, the Buddha's doctrine did have an important philosophical component: it negated the major claims of rival positions while building upon them at a new philosophical and religious level.
In a skeptical vein, he asserted the insubstantiality of the ego, and in doing so countered those Upanishadic sages who sought knowledge of an unchanging ultimate self. The Buddha created a new position in opposition to their theories, and held that attachment to a permanent self in this world of change is the cause of suffering and the main obstacle to liberation. The same skeptical approach negates the existence of any high god or essential substance, and undercuts both traditional and iconoclastic spiritual goals. He broke new ground by going on to explain the source for the apparent ego: it is merely the result of the aggregates (skandhas) which make up experience.
In this breaking down into constituent elements, the Buddha was heir to earlier element philosophies which had sought to characterize existing things as made up of a set of basic elements. The Buddha, however, eliminated mythological rhetoric, systematized world components into five groups, and used this approach not to characterize a substantial object, but to explain a delusion. He coordinated material components with psychological ones. The Buddha criticized the Brahmins' theories of an Absolute as yet another reification, instead giving a path to self-perfection as a means of transcending the world of name and form.