[Gr. theōria, viewing, spectacle, speculation]
A statement that best explains all the available evidence on a given topic. If evidence that contradicts the theory becomes available, the theory must be abandoned or changed to incorporate it. When a theory becomes generally accepted and firmly established, it may be called a doctrine or principle.

activity theory

A social theory of aging that asserts that the more active older persons are, the higher their satisfaction and morale. According to this theory, those who age successfully cultivate substitutes for former societal roles that they may have had to relinquish.

theory of aging

Any coherent set of concepts that explains the aging process at the cellular, biological, psychological, and sociological levels.

atomic theory

1. The theory that all matter is composed of atoms.
2. Any of the theories pert. to the structure, properties, and behavior of the atom.

autoimmune theory of aging

The theory that aging occurs because antibodies develop, attack, and destroy the normal cells in the body. According to this theory, a progressive deficiency in immunological tolerance results in the inability to distinguish self from foreign structures.

avalanche theory

The theory that nerve impulses are reinforced and thereby become more intense as they travel peripherally.

change theory

The use of coaching strategies to encourage people to alter their actions, behaviors, or feelings, esp. from a current dysfunctional state to a desired one. Planned change is a sequence of events implemented to achieve established goals. In nursing an agent of change is a person who advocates reforms that affect nursing services. The agent may be a nurse leader, a staff nurse, or someone who works with nurses.

clonal selection theory of immunity

The theory that precursor cell lines for lymphocytes are made up of innumerable clones with identical antigen receptors. The clones capable of reacting with autoantigenic components are eliminated or suppressed in the prenatal period. Those clones not eliminated or suppressed react only with specific foreign antigens that fit their receptors, leading to the proliferation of that lymphocyte cell line. Within the body, there are many different lymphocyte clones, each of which only reacts to one antigen (clonal restriction).

Cohnheim theory

SEE: Cohnheim, Julius Friedrich

theory of evolution

The theory that all living species, including humans, have developed as a result of changes in their genetic material over time.
SEE: natural selection

comfort theory

A middle range theory developed by Katherine Kolcaba that proposes that the relief of distress, sorrow, worry, grief, anxiety, and hopelessness are the primary goals of holistic nursing.

five-elements theory

five-element theory A fundamental premise in traditional Chinese medicine and some branches of alternative medicine that holds that illness results from imbalances in the five elements of wood, fire, earth, metal, and water. A similar concept in ancient Western and medieval medicine held that diseases resulted from imbalances in the four elements of earth, air, fire, and water.
SEE: feng shui

gate theory

The theory that painful stimuli may be prevented from reaching higher levels of the central nervous system by stimulation of larger sensory nerves. This is one of the proposed explanations of the action of acupuncture and of transcutaneous electrical nerve stimulation (TENS) units.

general system theory

The theory that all living systems are open systems constantly exchanging information, matter, and energy with the environment. There are three levels of reference for systems: the system level on which one is focusing, (such as a person); the suprasystems level above the focal system, (such as a person's family, community, and culture); and the subsystem, which is below the focal system, (such as the bodily systems and the cell). The theory suggests that the treatment of people is more important than the treatment of illnesses.
SEE: holistic medicine

germ theory

The theory that infectious diseases are caused by microorganisms.

grand theory

A set of abstract ideas that together make a broad statement about human beings, the environment, health, or nursing. A grand theory is broad in scope. It is made up of concepts and propositions that are less abstract and general than the concepts and propositions of a conceptual model but are not as concrete and specific as the concepts and propositions of a middle-range theory. A grand theory sometimes is used in place of a conceptual model as a guide for research or practice.

health belief theory

A theory of how and why people choose to make healthy choices in their lives. The theory suggests that people make such decisions intentionally, evaluating their risks for diseases, the likely severity of illnesses, and the potential benefits from taking action, and that they act when they perceive a clear benefit. Other theories about healthy behavior stress physiological or psychological reasons for health-related decisions.

theory of infinitesimals

One of Samuel Hahnemann's three “natural laws”: that properly diluted substances become more and more powerful as remedies the more dilute they become.

Lamarck theory

SEE: Lamarck theory

learning theory

The theory that learning occurs by application of laws of learning. Learning represents a change in behavior due to practice, education, and experience.

Maslow theory of human motivation

SEE: Maslow, Abraham H.

Metchnikoff theory

SEE: Metchnikoff theory

middle-range theory

A theory comprising limited numbers of variables, each of limited scope. Middle-range theories may be descriptive, explanatory (specifying relationships between two or more concepts), or predictive (envisioning relationships between concepts or effects of certain concepts on others). Examples include the Health Belief Model, the Theory of Maternal Attachment, the Erikson Theory of Psychosocial Development, Watson's Theory of Human Caring, and the Maslow Hierarchy of Needs Theory. Middle-range theories are made up of a limited number of concepts and propositions that are written at a relatively concrete and specific level. Middle-range theories are generated or tested by means of research, and are used as the evidence for practice activities, such as assessment and intervention.

normal accident theory

The assumption that accidents are inevitable in a complex working environment in which tasks are both difficult and constrained by time pressure.

nursing theory

A theory that describes, explains, or predicts a phenomenon of interest to nurses and nursing educators.

theory of planned behavior/reasoned action

ABBR: TpB A model used to explain health-seeking behavior that suggests that such behavior depends on personal intention. In this theory an intention to promote health develops from the specific attitudes one holds about the proposed choice, the social pressure one faces (such as peer pressure) if one were to make that choice, and one's sense of empowerment (such as the confidence one holds that one's choice will be faithfully translated into fruitful action).

protection motivation theory

ABBR: PMT A model to explain health-seeking or health-avoidance behavior. It suggests that a person makes health-related choices based on the perception of risks and self-efficacy or of his vulnerability to illness and capacity to take effective action to avoid harm.

theory of psora

One of Samuel Hahnemann's three “natural laws”: that most chronic diseases result from suppressed itching.

quantum theory

The theory that energy can be emitted in discrete quantities (quanta) and that atomic particles can exist only in certain energy states. Quanta are measured by multiplying the frequency of the radiation, v, by the Planck constant, h.

recapitulation theory

The theory that during development an individual organism goes through the same progressive stages as did the species in developing from the lower to the higher forms of life; the theory that ontogeny recapitulates phylogeny.

self-determination theory

A theory of human motivation and personality that purports to understand and explain human choices in social contexts, as influenced by that person's beliefs, needs, and desire to influence or be affected by his environment.

social cognitive theory

SEE: social cognitive theory

social learning theory

The theory that learning social standards and behavior occurs by observing and imitating others, e.g., family members, peers, or role models. Social learning also includes conforming, learning in context, and modeling. Theories of social learning were developed by the American psychologist, Albert Bandura, who used them, e.g., to explain the impact of media violence on the behavior of children and adolescents.

summation theory

The theory that excessive or intense stimulation of nerves will eventually produce a disagreeable sensation, i.e., of pain.

target theory

A model used in radiobiology to describe cellular and chromosomal injury caused by radiation. The disruption of some intracellular targets by radiation can produce mutations; the disruption of critical targets is lethal to the cell.

telomeric theory of aging

The theory that the progressive loss of genetic material that accompanies the shortening of the end regions of chromosomes with each cycle of cell replication serves as a clock that defines aging at the cellular level.

Young-Helmholtz theory

SEE: Young-Helmholtz theory