Boris Sidis (October 12, 1867 – October 24, 1923) was a Ukraine-born American psychologist and psychiatrist who studied under William James at Harvard University. His areas of study included hypnosis, suggestion, and the subconscious; multiple personality, sleep, laughter, and the treatment of psychopathic disease.
- Suggestibility varies as the amount of disaggregation, and inversely as the unification of consciousness.
- The Psychology of Suggestion: a Research into the Subconscious Nature of Man and Society (1889), p. 90
- The principle of recognition of evil under all its guises is at the basis of the true education of man.
- Philistine and Genius (1919)
Multiple Personality: an Experimental Investigation into Human Individuality (1904) 
- The course of evolution is to a greater integration of similarly functioning ganglia.
- p. 16
- The general tendency of evolution is from structure to function, from bondage to freedom of the individual elements.
- p. 26
The Foundations of Normal and Abnormal Psychology (1914) 
- Science is the description of phenomena and the formulation of their relations.
- p. 11
- Psychology is the science of psychic states both as to content and form, regarded from an objective standpoint, and brought in relation to the living corporeal individual.
- p. 39
- The psycho-physiological hypothesis is both inductively and deductively the sine qua non of the science of psychology.
- p. 86
- The man of genius whether as artist or thinker requires a mass of accidental variations to select from and a rigidly selective process of attention.
- p. 98
- Not purpose but chance is at the heart of mental life.
- p. 100
- The fact that psychology postulates an external material world and studies it in so far as it comes to be reflected in consciousness, points to another postulate which psychology must assume in addition, namely, the existence of an inner world consciousness.
- p. 106
- Psychology must postulate uniformity of interrelation of physical, physiological, and psychic processes.
- p. 112
- Mental synthesis of psychic content in the unity of a moment-consciousness is a fundamental principle of psychology.
- p. 117
The Causation and Treatment of Psychopathic Diseases (1916) 
- The main source of psychopathic diseases is the fundamental instinct of fear with its manifestations, the feeling of anxiety, anguish, and worry.
- p. 33
- Superstitions, and especially the early cultivation of religion, with its “fear of the Lord” and of unknown mysterious agencies, are especially potent in the development of the instinct of fear. Even the early cultivation of morality and conscientiousness, with their fears of right and wrong, often causes psychoneurotic states in later life. Religious, social, and moral taboos and superstitions, associated with apprehension of threatening impending evil, based on the fear instinct, form the germs of psychopathic affections.
- p. 37
The Source and Aim of Human Progress (1919) 
- It is not the citizen, or a taxpayer, or voter, or office-holder, but the cultivated, free individual who is the true aim of all social progress.
- No opinion should be disdained and scorned.
- If society is to progress on a truly humanistic basis, without being subject to mental epidemics and virulent social diseases to which the subconscious falls an easy victim, the personal consciousness of every individual should be cultivated to the highest degree possible.
- Greatness of individuality is inversely proportional to the mass of the social aggregate.
- A social aggregate which has chosen the fatal path of organic evolution must succumb to the same law of organic development to which all organisms are subject, namely greater and greater organization, increase of structure, greater differentiation, decrease of critical, personal, consciousness, loss of individual liberty, increased activity of the subconscious forces, falling into a state of somnambulism which can only be redeemed by revolution or by death.
- If ceaseless vigilance is the price of liberty, more so is it true that ceaseless criticism of ever new opinions and ever new views, however distasteful, bizarre, and paradoxical, is the price of truth.
- The freedom of the seemingly false opinion and our tolerance of it and our willingness to meet with it in the open help test the validity of truth while keeping alive the critical sense which is the main spring of all advancement of human thought and is the vital point, the very soul, of all human progress.
Nervous Ills their Cause and Cure (1922) 
- Self-preservation is the central aim of all life-activities.
- p. 20
- The tendency of life is not the preservation of the species, but solely the preservation of each individual organism, as long as it is in existence at all, and is able to carry on its life processes.
- p. 20
- The recognition, the diagnosis, and the preservation of psychopathic individuals account for the apparent increase of neurotics in civilized communities.
- p. 275
- It is time that the medical and teaching profession should realize that functional neurosis is not congenital, not inborn, not hereditary, but is the result of a defective, fear-inspiring education in early child life.
- p. 285
- Human institutions depend for their existence and stability on the impulse of self-preservation and its close associate, — the fear instinct.
- p. 311
- The Boris Sidis Archive at the Sidis website