Epoché (ἐποχή epokhē, "suspension"^[1]) is an ancient Greek term typically translated as "suspension of judgment" but also as "withholding of assent".^[2] The term is used in slightly different ways among the various schools of Hellenistic philosophy.

The Pyrrhonists developed the concept of "epoché" to describe the state where all judgments about non-evident matters are suspended in order to induce a state of ataraxia (freedom from worry and anxiety). The Pyrrhonist philosopher Sextus Empiricus gives this definition: "Epoché is a state of the intellect on account of which we neither deny nor affirm anything."^[3] This concept is similarly employed in Academic Skepticism, but without the objective of ataraxia.

In Stoicism the concept is used to describe the withholding of assent to phantasiai (impressions). For example Epictetus uses the term in this manner: "If what philosophers say is true, that in all men action starts from one source, feeling, as in assent it is the feeling that a thing is so, and in denial the feeling that it is not so, yes, by Zeus, and in epoché, the feeling that it is uncertain: so also impulse towards a thing is originated by the feeling that it is fitting, and will to get a thing by the feeling that it is expedient for one, and it is impossible to judge."^[4]

Epoché plays an implicit role in subsequent philosophical skeptic thought, as in René Descartes' epistemic principle of methodic doubt. The term was popularized in modern philosophy by Edmund Husserl. Husserl elaborates the notion of 'phenomenological epoché' or 'bracketing' in Ideas I. Through the systematic procedure of 'phenomenological reduction', one is thought to be able to suspend judgment regarding the general or naive philosophical belief in the existence of the external world, and thus examine phenomena as they are originally given to consciousness.^[5]

Epoché plays an important role in Pyrrhonism, the skeptical philosophy named after Pyrrho. Pyrrhonism provides practitioners with techniques for achieving epoché through use of the Ten Modes of Aenesidemus, the Five Modes of Agrippa, and the Pyrrhonist maxims.^[6] Pyrrhonism is mostly known today through the writings of the Pyrrhonist philosopher Sextus Empiricus whose surviving works appear to be an encyclopedia of Pyrrhonist arguments for inducing epoché across a breadth of philosophical and other intellectual issues of antiquity.

In phenomenological research epoché is described as a process involved in blocking biases and assumptions in order to explain a phenomenon in terms of its own inherent system of meaning. This is a general predisposition one must assume before commencing phenomenological study. It is different from bracketing, which is to acknowledge any personal bias or contextual assumptions of the researcher. This involves systematic steps to "set aside" various assumptions and beliefs about a phenomenon in order to examine how the phenomenon presents itself in the world of the participant.^[7]