“since all phenomena, including persons, exist only as causally connected continua, and since the causes and conditions of any episode in any continuum are themselves dependent on indefinitely many causes and conditions, both within and external to the conventionally identified continuum of a person or an object, all things exist only in thoroughgoing interdependence on countless other things. In short, things arise in dependence on innumerable causes and conditions; endure in dependence on innumerable causes and conditions; and cease in dependence on innumerable causes and conditions.”

[…]

dependent origination does not only involve causal interdependence. It is often characterized as tridimensional. The first dimension is the causal dimension emphasized so far. But second, there is synchronic interdependence between any whole and the parts in which it consists. Any complex depends for its existence and character on its parts; its parts, in turn, depend on the wholes that they comprise. I rely on my stomach, lungs, brain, and bone for my existence, but none of these could exist or function were it not part of a whole organism. Finally, in virtue of the lack of any intrinsic identity in spatiotemporally extensive entities, everything that we identify as a thing, once again including ourselves, depends for that identity—and so, for the only existence it has as an enduring or distinct entity—on conceptual designation. The only thing that makes a table a table is a convention that collects four legs and a top into a single entity as a referent for the word “table.” [cf. neurophenomenology of time]

All of this grounds the idea whose articulation is so central to Buddhist philosophy in the Mahayana schools that dominate later Indian and all Tibetan and East Asian Buddhist philosophy—the emptiness of all things. It is easy to misunderstand the claim that everything is empty. In order to avoid the most basic and tempting misunderstanding, namely, that this is a doctrine of universal nihilism, it is important to remember that to be empty is always to be empty of something. In a Buddhist context, reality is not empty of existence, but is empty of inherent existence, or of essence (svabhava). On this view, conventional phenomena exist, but they do not exist with essences. Nothing is independent of causes and conditions, part-whole relations, or conceptual imputation; nothing is permanent; nothing has any characteristic on its own that makes it the thing that it is. Things, according to proponents of these systems, are empty of all of that. Having said this, there is considerable dispute within the tradition regarding the relevant notion of essence, and regarding just what it is to be empty in the relevant sense.

Recognizing the emptiness of all phenomena conceptually is, according to most Buddhist philosophers, not all that difficult: good philosophical analysis will suffice. But coming to perceive and to recognize phenomena as empty, most would argue, is a difficult achievement. It requires extirpating deep-seated impulses to reify ourselves and others, to regard ourselves and others as permanent, as consisting of a substantial core over which properties are laid, and to regard ourselves and others as essentially independent and only accidentally interacting agents and objects. These are the delusions, Siddhartha Gautama argued, that trap us in suffering.

The fact that everything exists in a causally interdependent, conventional way but is at the same time ultimately empty grounds the doctrine of the two truths. The first truth is the conventional, or concealing (samvrti, vyavahara) truth or reality (satya); the second is the ultimate (paramartha) truth or reality. Conventional truth is the realm of persons, objects, dogs, cats, trees, tables, and hard currency. Conventionally, objects exist, endure, and have a whole range of fascinating properties. But ultimately, they are empty. They exist only as impermanent, conventional designations, as we can see when we pursue careful philosophical analysis. The conventional truth is what appears to uncritical consciousness, and is regarded as deceptive, in that conventional phenomena appear to ordinary folks as though they exist inherently, even though they do not. The ultimate truth is what appears on careful analysis, or to those who have cultivated their cognitive powers to the point where they apprehend things spontaneously as empty. When things appear in this way, they appear nondeceptively.

Much of Buddhist thought is dedicated to understanding the complex relation between the two truths, and there is much diversity of opinion on this question. It is important, however, to note that they are presented as two truths, not as truth and falsehood, or as appearance and reality. Working out how this can be the case is no easy matter. Part of the agenda is set for the Mahayana schools by the famous declaration in the Heart of Wisdom Sutra that “form is empty; emptiness is form; emptiness is not different from form; form is not different from emptiness.” In some deep sense, on this view, the two truths are one. To be conventionally real is to be empty of inherent existence; to be empty of inherent existence is what it is to be conventionally real.

Buddhist debates concerning the nature of reality and truth naturally lead to concern with questions of how knowledge is attained. For the most part, Buddhist philosophers have argued that perception and inference are the only valid sources of knowledge; first-person verification is systematically valorized over the authority of scriptures or teachers. Ultimately, though, because most Buddhist philosophers believe that words can only denote nonexistent universals, and the particulars that actually exist are inexpressible, they argue that since inference is always verbal and conceptual, and therefore engaged with the nonexistent, even inference is to be abandoned by the awakened mind. The Buddha, however, employed language to teach the Dharma, and Buddhist philosophers have devoted much attention to considering how linguistic meaning is achieved and how language should be employed on the Buddhist path. For some, the answer to the question of how to use language has resulted in systematic treatises that proceed via linguistic argument, inference, and conceptual thought. For others, the only way to point to the linguistically inexpressible truth has been through employing enigmatic silence or the provocative, and noninferential, use of language found in the koan. While Buddhists understand insight into the nature of reality to be necessary for liberation, it is generally not regarded as sufficient. Insight is an antidote to ignorance, but liberation also requires the overcoming of attachment and aversion, which is achieved through the cultivation of moral discipline and mindfulness. For this reason Buddhists have devoted much thought to the question of which acts, intentions, consequences, virtues, and states of mind lead to this kind of mental transformation and thereby the alleviation of suffering. In moral thought, there is more agreement than in other areas of Buddhist philosophy, yet there is still a great diversity of approaches to moral questions in Buddhist traditions. These include elements that resemble virtue ethics, deontology, and utilitarianism, but Buddhist ethics is best approached on its own terms rather than as a species of one of the Western traditions. It is best characterized as a kind of moral pluralism, as a sustained effort to solve a fundamental existential problem using a variety of means. Its scope is sometimes broader than that of Western ethical theory, inasmuch as such cognitive states as ontological confusion are regarded as moral, and not simply as epistemic failings; and sometimes narrower, taking vows as grounding fundamental moral concerns, as opposed to general sets of obligations. Many important debates in contemporary Buddhist moral thought concern the relation between Buddhist ethics and questions of social, political and economic justice.”