It seems that many people say that hypnosis and meditation are very similar. But what are their key differences (both in a soft and hard way)?
I believe this question is impossible to "answer" because the inherent premises in the question are based on the assumption that there are two discrete dichotomous phenomena, "hypnotism," and "meditation," which can somehow be meaningfully "defined," and, then, "compared."
Both "hypnosis" and "meditation" are figuratively vast conceptual collages of imprecise multiple-meanings, observations of what appear to be "special" states of human awareness, and consciousness, admixtures from what in "western science" is termed "psychology" with an equally vast mix of practices, lumped-together as "spiritual," from the world's religions, etc.
From the viewpoint of epiphenomenal philosophy ... wikipedia entry ..., and from some modern, western, theorists of human consciousness as grounded in our biological, neurological, reality, both hypnosis and meditation can be regarded as secondary phenomena: in the sense that they are culturally defined and shaped modes of thought, behavior, and experience, in a "continuum of consciousness," which, over time, are conserved, institutionalized, even valorised into being perceived as "sacred."
In Vipassana meditation, in the Theravadan Buddhist tradition (Sanskrit "sthaviravada," "teachings of the elders") one way the "anti-goal" of meditation could be defined is: it is a practice meant as a vehicle for the de-hypnosis of the "illusory personal, small, self," leading to a direct experience of the "real, undifferentiated, trans-personal Self."
But, in that tradition, in its "purest" form, meditation is not a "goal in itself," and meditation is not a "means to an end" of achieving "altered states of consciousness."
But, there are countless other types, schools, philosophies, of "meditation," with very different conceptual underpinnings, some "secular," some "formally religious," and a wide range of behavioral practices associated with them.
On the "grossest" level, you might say we observe, when we see what appears to be hypnosis of one person by another, a loss of conscious, and subconscious, control of self from the person hypnotized to the hypnotist. But, then: there's stage hypnosis, self-hypnosis, so-called therapeutic hypnosis for behavior modification (such as giving up smoking, etc.).
While we typically associate meditation with acts of what we define, in western psychological terms, as individual "self-control," and "discipline," there are traditions in which group practices (rituals) leading to mass ecstasy are considered meditation (Sufi Zhikr ?).
From one perspective, "cultural identity," itself, can be considered a cohesive set of internalized hypnotic states of mind: continually reinforced from within, and without, the self, and modified in biological development throughout the life-cycle ... I am not referring, here, to the movie-series, "The Matrix" :) !
Hypnotism and psychotherapy: Milton Erickson ... Amazon page ....
Psychology and consciousness: books by Robert Ornstein ... Ornstein's website ...; books by Andrew Weill ... Weill's Amazon page ..., books by Steven Pinker, particularly, "The Language Instinct" ... Pinker's website ....
Meditation and Buddhism:
a. Donald Lopez ... "The Story of Buddhism: A Concise Guide to Its History & Teachings" ...: excellent overview of how original Buddhism became "modified:" incorporated a mixture of Vedic/Hindu classic ideas (influence of Advaita Vedanta, and Yogacara schools, for example); incorporated Sivaite Tantra as developed in what is now Bengal; and, later, became "deistic," with an elaborate hierarchic pantheon, in India, Tibet, China, Japan (into what can be loosely lumped together under the rubric "Mahayana Buddhism"). Depending on your biases, you might say, rather than "modified:" "evolved," or "corrupted.."
b. Theravadan Buddhist tradition (Sri Lanka, Southeast Asia), and Vipassana meditation (aka "mindfulness", or "insight" meditation): Walpole Rahula ... "What the Buddha Taught: Revised and Expanded Edition" ...; Thich Nhat Hanh ... Amazon page ...; books by Joseph Goldstein ... recommended: "Insight Meditation: The Practice of Freedom" ...; books by Bernard Kornfeld ... Amazon page ....
Main difference is that the meditation is self-induced and with full self-awareness, whereas hypnosis is usually induced by another person (unless is self-hypnosis which is self-induced) and the person is in state of trance, amnesia or unconscious.
Hypnosis is defined by the U.S government as "the bypass of the critical factor of the conscious mind and the establishment of acceptable selective thinking.". Hypnosis can help you in various ways and is a calm state of altered-consciousness that allows a person to recall memories or be guided to change a behavior (in example to help someone stop smoking).
While meditation is a practice in which an individual trains the mind or induces a mode of consciousness. An ordinary person may be consider meditation as a prayer or total stillness, but the goal of meditation is to focus and quiet your mind, eventually reaching a higher level of awareness and inner calm.
According to some beliefs or movements, the meditation from ancient times is the method of communication with other realms/planes of existence (Sephiroth) and entities (higher self, astral beings, dead relatives, demons, aliens, ascended masters, angels, God, etc.), astral travel, remote viewing, clairvoyance or altering your body (Reiki, activating chakras, 3rd eye or DNA activation) or time-space reality (psychokinesis, telekinesis, teleportation, opening portals) and many more.
Whereas hypnosis was introduced to European society in 18th century and it is sometimes described as black magic and dangerous for our body and spirit, because the person is just the victim on stage with implanted suggestion by hypnotist. If it's done incorrectly, the victim suffers nightmares and aberrant behaviour.
Both the terms hypnosis and meditation are nebulous terms and are incomparable. There are many Hypnotic States, including the one called 'waking state'. There are many ways to define a hypnotic state, one of them is having a single point of focus to the exclusion of all other stimuli. This would follow the definition of James Braid of 'Monoideaism'. This would also be similar to a meditative state brought about by focusing attention on one thing such as the breathe, heart beat or ringing of a bell.
However if you look at volunteers at a hypnotists stage show they are up walking around, hallucinating images, sounds and feelings, this looks nothing like meditation and yet they would be considered to be 'in hypnosis'.
If we look at self-hypnosis and compare that to meditation, they are similar. The states are similar the process to get into that state of trance is similar and how they are used to change the brain are similar.
The biggest difference I can see between self-hypnosis and meditation is that meditation is viewed as a fixed teaching coming from ancient practices where as hypnosis is a growing body of knowledge.
Other differences are: That hypnotists tend to use relaxation as a means to coax the mind to move from a defensive posture to a receptive posture while meditative practices cultivate focusing the mind on discarding or ignoring other stimuli.
Self hypnosis is goal specific orientated, the goal is to relax, take in a new suggestion or be in a state of repair. As a result of being goal orientated, self hypnosis can be trained by a hypnotist in a matter of minutes. Meditation from ancient practices in contrast, is intended to be a lifelong practice with skills built up the foundations of the previous skills and the benefits are non specific.
There is a clear answer in terms of the biblical model of psychology: they are exact opposites. There is body, soul, and spirit. Picture the soul as a garden, where experiences, thoughts and habits are planted and cultivated. The spirit is the gardener. In hypnotism, the spirit or gardener is put to sleep so someone else can temporarily come into the garden and plant seeds, dig up plants, etc. In meditation, the soul is put to sleep so the spirit can do some gardening. Most people are in a hypnotic state most of the time though, meaning their gardener is asleep on the job, so meditation serves to wake up the gardener. So it comes to the give a man a fish/teach him to fish metaphor. Hypnotism is getting a fish (or maybe a snake) and meditation is learning to fish. Also for closure in the garden metaphor, the body and external circumstances are the harvest from your garden.