Following the French committee's findings, in his Elements of the Philosophy of the Human Mind (1818),  Dugald Stuart, an influential academic philosopher of the "Scottish School of Common Sense", encouraged physicians to salvage elements of Mesmerism by replacing the supernatural theory of "animal magnetism" with a new interpretation based upon "common sense" laws of physiology and psychology. Braid quotes the following passage from Stewart:
It appears to me, that the general conclusions established by Mesmer’s practice, with respect to the physical effects of the principle of imagination [...] are incomparably more curious than if he had actually demonstrated the existence of his boasted science [of "animal magnetism"]: nor can I see any good reason why a physician, who admits the efficacy of the moral [i.e., psychological] agents employed by Mesmer, should, in the exercise of his profession, scruple to copy whatever processes are necessary for subjecting them to his command, any more than that he should hesitate about employing a new physical agent, such as electricity or galvanism.
In Braid's day, the "Scottish School of Common Sense", provided the dominant theories of academic psychology and Braid refers to other philosophers within this tradition throughout his writings. Braid, therefore, revised the theory and practice of Mesmerism and developed his own method of "hypnotism" as a more rational and "common sense" alternative.
It may here be requisite for me to explain, that by the term Hypnotism, or Nervous Sleep, which frequently occurs in the following pages, I mean a peculiar condition of the nervous system, into which it may be thrown by artificial contrivance, and which differs, in several respects, from common sleep or the waking condition. I do not allege that this condition is induced through the transmission of a magnetic or occult influence from my body into that of my patients; nor do I profess, by my processes, to produce the higher [i.e., supernatural] phenomena of the Mesmerists. My pretensions are of a much more humble character and are all consistent with generally admitted principles in physiological and psychological science. Hypnotism might therefore not inaptly be designated, Rational Mesmerism, in contra-distinction to the Transcendental Mesmerism of the Mesmerists.
Despite briefly toying with the name "rational Mesmerism", Braid ultimately emphasised his approach's uniqueness, carrying out informal experiments throughout his career to refute the arguments invoking supernatural practices, and demonstrate instead the role of ordinary physiological and psychological processes such as suggestion and focused attention in producing the observed effects.
Braid worked very closely with his friend and ally the eminent physiologist Professor William Benjamin Carpenter, an early neuro-psychologist, who introduced the "ideo-motor reflex" theory of suggestion. Carpenter had observed examples of expectation and imagination apparently influencing involuntary muscle movement. A classic example of the ideo-motor principle in action is the so-called "Chevreul pendulum" (named after Michel Eugene Chevreul). Chevreul claimed that divinatory pendular were made to swing by unconscious muscle movements, brought about by appropriate concentration alone.
Braid soon assimilated Carpenter's observations into his own theory, realising that the effect of focusing attention was to enhance the ideo-motor reflex response. Braid extended Carpenter's theory to encompass the influence of the mind upon the body more generally, beyond the muscular system, and therefore referred to the "ideo-dynamic" response and coined the term "psycho-physiology" to refer to the study of general mind/body interaction.
In his later works, Braid reserved the term "hypnotism" for cases in which subjects entered a state of amnesia resembling sleep. For the rest, he spoke of a "mono-ideodynamic" principle to emphasise that the eye-fixation induction technique worked by narrowing the subject's attention to a single idea or train of thought ("monoideism"), which amplified the effect of the consequent "dominant idea" upon the subject's body by means of the ideo-dynamic principle.
Although he preceded Braid, his contribution gave great weight to the development of Hypnosis as we know it today.
Franz Mesmer (1734–1815) believed that there is a magnetic force or "fluid" within the universe that influences the health of the human body. He experimented with magnets to influence this field and, so, cause healing. By around 1774, he had concluded that the same effects could be created by passing the hands, at a distance, in front of the subject's body, referred to as making "Mesmeric passes." The word mesmerize originates from the name of Franz Mesmer, and was intentionally used to separate its users from the various "fluid" and "magnetic" theories embedded within the label "magnetism".
In 1784, at the request of King Louis XVI, a Board of Inquiry started to investigate whether Animal Magnetism existed. Three of the board members include a founding father of modern chemistry Antoine Lavoisier, Benjamin Franklin and an expert in pain control Joseph-Ignace Guillotin. They investigated the practices of a disaffected student of Mesmer, one Charles d'Eslon (1750–1786), and despite the fact that they accepted that Mesmer's results were valid, their placebo-controlled experiments following d'Eslon's practices convinced them that mesmerism was most likely due to belief and imagination rather than to any sort of invisible energy ("animal magnetism") transmitted from the body of the mesmerist.
In writing the majority opinion, Franklin said, "This fellow Mesmer is not flowing anything from his hands that I can see. Therefore, this mesmerism must be a fraud." Mesmer left Paris and went back to Vienna to practise mesmerism.
Braid's peers and Hysteria vs. suggestion
For several decades, Braid's work became more influential abroad than in his own country, except for a handful of followers, most notably Dr John Milne Bramwell. The eminent neurologist Dr George Miller Beard took Braid's theories to America. Meanwhile, his works were translated into German by Wilhelm T Preyer, Professor of Physiology at Jena University. The psychiatrist Albert Moll subsequently continued German research, publishing Hypnotism in 1889. France became the focal point for the study after the eminent neurologist Dr. Etienne Eugene Azam presented Braid's research to the French Academy of Sciences. Azam also translated Braid's last manuscript (On Hypnotism, 1860) into French. At the request of Azam, Paul Broca and others, the French Academy of Science, who had examined Mesmerism in 1784, examined Braid's writings shortly after his demise.
Azam's enthusiasm for hypnotism influenced Ambrose-Auguste Liebeault, a country doctor. Hippolyte Bernheim discovered Liébeault's enormously popular group hypnotherapy clinic and subsequently became an influential hypnotist. The study of hypnotism subsequently revolved around the fierce debate between Jean-Martin Charcot and Hippolyte Bernheim, the two most influential figures in late 19th-century hypnotism.
Charcot operated a clinic at the Pitie=Salpetiere Hospital (thus, also known as the "Paris School" or the "Salpêtrière School"), while Bernheim had a clinic in Nancy (also known as the "Nancy School"). Charcot influenced more by the Mesmerists, argued that hypnotism is an abnormal state of nervous functioning found only in certain hysterical women. He claimed that it manifests in a series of physical reactions that could be divided into distinct stages. Bernheim argued that anyone could be hypnotised, that it is an extension of normal psychological functioning, and that its effects are due to suggestion. After decades of debate, Bernheim's view dominated. Charcot's theory is now just a historical curiosity.
Charcot is best known today, outside the community of neurologists, for his work on hypnosis and hysteria. He believed that hysteria was a neurological disorder for which patients were pre-disposed by hereditary features of their nervous system. Charcot's interest in hysteria and hypnotism "developed at a time when the general public was fascinated by 'animal magnetism' and mesmerization' ... Charcot and his school considered the ability to be hypnotized as a clinical feature of hysteria ... For the members of the Salpêtrière School, susceptibility to hypnotism was synonymous with disease, i.e. hysteria, although they later recognized ... that grand hypnotisme (in hysterics) should be differentiated from petit hypnotisme, which corresponded to the hypnosis of ordinary people".
The Salpêtrière School's position on hypnosis was sharply criticized by Hippolyte Bernheim, a leading neurologist of the time. Charcot himself long had concerns about the use of hypnosis in treatment and about its effect on patients. He also was concerned that the sensationalism hypnosis attracted had robbed it of its scientific interest, and that the quarrel with Bernheim, further mostly by his pupil Georges Gilles de la Tourette, had "damaged" hypnotism
When the medical faculty took up hypnotism, about 1880, Bernheim was very enthusiastic, and soon became one of the leaders of the investigation. He became a well-known authority in this new field of medicine.
Albert Moll (1862–1939), an active promoter of hypnotism in Germany, went to Nancy and studied with Bernheim; while in the States, Boris Sidis and Morton Prince were also considered part of the Nancy School.
Bernheim also had a significant influence on Sigmund Freud, who had visited Bernheim in 1889, and witnessed some of his experiments (though he was known as an antagonist of Jean-Martin Charcot with whom Freud had studied in Paris). Freud had already translated Bernheim's On Suggestion and its Applications to Therapy in 1888; and later described how "I was a spectator of Bernheim's astonishing experiments upon his hospital patients, and I received the most profound impression of the possibility that there could be powerful mental processes which nevertheless remained hidden from the consciousness of man". He would later term himself a pupil of Bernheim, and it was out of his practice of Bernheim's suggestion/hypnosis that psychoanalysis would evolve.
Bernheim himself increasingly turned from hypnosis to the use of suggestion in a waking state, something his school began to term 'psychotherapeutics'.
Pierre Janet (1859–1947) reported studies on a hypnotic subject in 1882. Charcot subsequently appointed him director of the psychological laboratory at the Salpetriere in 1889, after Janet completed his doctorate in philosophy, which dealt with psychological Automatism. In 1898, Janet was appointed psychology lecturer at the Sorbonne, and in 1902 became chair of experimental and comparative psychology at the College de France. Janet reconciled elements of his views with those of Bernheim and his followers, developing his own sophisticated hypnotic psychotherapy based upon the concept of psychological dissociation, which, at the turn of the century, rivalled Freud's attempt to provide a more comprehensive theory of psychotherapy.
Sigmund Freud, the founder of psychoanalysis, studied hypnotism at Paris school and briefly visited the Nancy school.
At first, Sigmund Freud was an enthusiastic proponent of hypnotherapy and soon began to emphasise hypnotic regression and ab reaction (catharsis) as therapeutic methods. He wrote a favourable encyclopedia article on hypnotism, translated one of Bernheim's works into German, and published an influential series of case studies with his colleague Joseph Breuer entitled Studies on Hysteria (1895). This became the founding text of the subsequent tradition known as "hypno-analysis" or "regression hypnotherapy."
However, Freud gradually abandoned hypnotism in favour of psychoanalysis, emphasizing free association and interpretation of the unconscious. Struggling with the great expense of time that psychoanalysis required, Freud later suggested that it might be combined with a hypnotic suggestion to hasten the outcome of treatment,
It is very probable, too, that the application of our therapy to numbers will compel us to alloy the pure gold of analysis plentifully with the copper of direct [hypnotic] suggestion.
However, only a handful of Freud's followers were sufficiently qualified in hypnosis to attempt the synthesis. Their work had a limited influence on the hypnotherapeutic approaches now known variously as "hypnotic regression", "hypnotic progression", and "hypnoanalysis".
Emile Coue (1857–1926) assisted Ambrose-Auguste Liebeault for around two years at Nancy. After practising for several years as a hypnotherapist employing the methods of Liébeault and Bernheim's Nancy School, Coué developed a new orientation called "conscious autosuggestion." Several years after Liébeault's death in 1904, Coué founded what became known as the New Nancy School, a loose collaboration of practitioners who taught and promoted his views. Coué's method did not emphasise "sleep" or deep relaxation and instead focused upon autosuggestion involving a specific series of suggestion tests. Although Coué argued that he was no longer using hypnosis, followers such as Charles Baudouin viewed his approach as a form of light self-hypnosis. Coué's method became a renowned self-help and psychotherapy technique, which contrasted with psychoanalysis and prefigured self-hypnosis and cognitive therapy.
Clark L. Hull
The next major development came from behavioural psychology in American university research. Clark L Hull, an eminent American psychologist, published the first major compilation of laboratory studies on hypnosis, Hypnosis & Suggestibility (1933), in which he proved that hypnosis and sleep had nothing in common. Hull published many quantitative findings from hypnosis and suggestion experiments and encouraged research by mainstream psychologists. Hull's behavioural psychology interpretation of hypnosis, emphasizing conditioned reflexes, rivalled the Freudian psycho-dynamic interpretation emphasizing unconscious transference.
Although Dave Elman was a noted radio host, comedian and (song)writer, he also made a name as a hypnotist. He led many courses for physicians and wrote in 1964 the classic book: 'Findings in Hypnosis', later to be re-titled 'Hypnotherapy' (published by Westwood Publishing). Perhaps the most well-known aspect of Elman's legacy is his method of induction, which was originally fashioned for speed work and later adapted for the use of medical professionals; his students routinely obtained states of hypnosis adequate for medical and surgical procedures in under three minutes. His book and recordings provide much more than just his rapid induction techniques, however. The first heart operation using hypnosis rather than normal anaesthesia (because of severe problems with the patient) was performed by his students with Dave Elman in the operating room as "coach".
Milton H Erickson, M.D. was one of the most influential post-war hypnotherapists. He wrote several books and journal articles on the subject. During the 1960s, Erickson popularized a new branch of hypnotherapy, known as Ericksonian hypnotherapy, characterised primarily by indirect suggestion, "metaphor" (actually analogies), confusion techniques, and double binds in place of formal hypnotic inductions. However, the difference between Erickson's methods and traditional hypnotism led contemporaries such as Andre Weitzenhoffer, to question whether he was practising "hypnosis" at all, and his approach remains in question.
Erickson had no hesitation in presenting any suggested effect as being "hypnosis", whether or not the subject was in a hypnotic state. In fact, he was not hesitant in passing off behaviour that was dubiously hypnotic as being hypnotic.