Answer
Hesychasm is a form of Christian mysticism found almost exclusively in Eastern Orthodoxy, rising to popularity in Greece in the 1300s. Roman Catholicism and Protestant denominations have no meaningful equivalents to it. Hesychasm has many similarities to Buddhist concepts of meditation, but it maintains a Judeo-Christian framework, rather than a pantheistic one. The general idea in Hesychasm is to use contemplative prayer, particularly the repetition of “the Jesus Prayer,” as a means to experience union with God. This requires the Hesychast to block out all his senses and eliminate all his thoughts.
Hesychasm is, supposedly, grounded in Jesus’ command in Matthew 6:6. There, Jesus refutes the ostentatious prayers of hypocrites who want to be seen praying in public. Instead, Jesus says, “Go into your room, close the door and pray to your Father, who is unseen. Then your Father, who sees what is done in secret, will reward you.” Hesychasts take Jesus’ reference to secret praying in an extreme and absolute sense. In particular, they believe that Jesus intended His followers to separate themselves from all sensory and intellectual inputs. In other words, “go into your room,” really means “go into yourself.”
This withdrawal into oneself is accomplished by a form of repetitive contemplative prayer. The Jesus Prayer is a short, liturgical chant very popular in Eastern Orthodoxy: Κύριε Ἰησοῦ Χριστέ, Υἱὲ τοῦ Θεοῦ, ἐλέησόν με τὸν ἁμαρτωλόν (“Lord Jesus Christ, Son of God, have mercy on me, a sinner”). Hesychasts will repeat this prayer over and over, seeking to invoke the power of the name of God. As they do so, practitioners gradually cut off their perception of external stimuli and eliminate all stray thoughts. The ultimate goal of this process is theosis, a personal unity with God.
Hesychasm considers prayers in four categories of ascending value: verbal prayer, mental prayer, heart prayer, and contemplation. Each type of prayer is successively more internal, more separated from external stimuli. The ultimate expression of contemplation is a total absence of sensory awareness, a complete lack of personal thought, and a pure connection to God.
Hesychastic methods are similar, in many ways, to Eastern meditation practices. Repetitive words or thoughts in a quest to banish independent thought, reject external stimulus, and shed desires are essential aspects of pantheistic meditation practices. The goal of separating oneself from the outside world is also a common component of Eastern mysticism.
Hesychasm, however, is neither pantheistic nor truly compatible with such worldviews. Unlike a Buddhist or Hindu, the Hesychast is not trying to achieve a state of non-being. Rather, the desired theosis is a “unity” with God similar to what is experienced between the members of the Trinity. Another difference is in the use of the Jesus Prayer. In Hesychasm, the meaning of the words, not the syllables, is important. So the phrase can be prayed in any language, as long as the practitioner focuses on the intended meaning of the sentence.
Mysticism is based on the quest to “experience” God through the use of rituals or other techniques. All forms of mysticism are rooted in an assumption that God can only truly be “known” in some subjective or personal way. Contrary to mysticism in general, and Hesychasm in particular, the Bible commands us to pray with a purpose and intent, not with a goal of washing out our own thoughts (Philippians 4:6; John 16:23–24). Scripture also indicates that God can be known objectively—or else it would not be possible to “examine” or “test” our own faith (1 John 4:1; 2 Corinthians 13:5).
Jesus’ comment in Matthew 6:6 was never meant to be taken as a command to go “within ourselves.” It was and is simply a refutation of hypocritical and showy religious antics. While Hesychasm is not quite the same as Eastern meditative practices, it is neither biblical nor beneficial.