Nursing theory has evolved since Florence Nightingale founded modern nursing. The purposes of nursing theory are to define nursing, describe what nurses do, and provide goals or outcomes of care. A theory is a set of concepts and propositions that provides an orderly way to view phenomena. Theories are made up of concepts and propositions. Concepts are mental images of a phenomenon and propositions describe relationships between concepts.

A conceptual framework is the structure that links concepts together, representing a unified whole. A conceptual model is a symbolic representation of a theory, shown through diagrams, words, or mathematical notations. Nursing theory has helped the profession categorize and communicate knowledge. Nurses test theories by conducting nursing research by studying the concepts and propositions described by nurse theorists.

Nursing is a discipline, a recognized field of study. Nurses have borrowed from biological, physical, and behavioral science disciplines to derive nursing theory. For example, nurses have borrowed both Maslow’s Hierarchy of Human Needs and Von Bartlaffny’s general systems theory to describe nursing phenomena.

Nursing theories describe phenomena in nursing practice and research tests those theories. The results of nursing research are then applied to nursing practice. Standards of nursing care arise from nursing theories and research. Research questions also arise out of nursing practice. Deciding on a nursing theory to use or to research requires careful study of the problem or question. When they have selected a research problem or question, nurses derive knowledge through Carper’s (1978) patterns of knowing: empirical (scientific) knowledge, aesthetic (creative) knowledge, personal knowledge, and ethical knowledge.

Theories can be either grand in scope, dealing with global and complex phenomena, or more limited. Grand theory provides an overall framework for structuring ideas. Middle-range theory addresses more narrowly defined phenomena and can be used to suggest an intervention. Specific theories of a discipline form a paradigm (a particular viewpoint or perspective). Nursing has undergone a paradigm shift, from a mechanistic (cause-and-effect) point of view to a holistic (humanistic) point of view. The metaparadigm concepts of a discipline are the phenomena of concern, or domains, of that discipline. The metaparadigms of nursing are: Person, health, environment, and nursing. The person can be either an individual or a family.

Florence Nightingale is recognized as the first nurse theorist. She described nursing as both an art and a science. She recommended adjusting the environment to improve the person’s health. Subsequent nurse theorists can be classified as early, contemporary, and new worldview nursing theorists. Early nursing theorists developed their ideas in the 1950s, focusing on nursing tasks or the interpersonal relationship between the nurse and the client. Virginia Henderson defined nursing as assisting the individual to gain health or to be allowed a peaceful death. Along with Bertha Harmer, she wrote a fundamentals of nursing text that described 14 human needs addressed by nurses. Faye Abdellah expanded Henderson’s 14 human needs into 21 nursing problems. Hildegard Peplau, a psychiatric nurse instructor, described the nurse-client relationship. Joyce Travelbee focused on the interpersonal relationship between the client and the nurse. Paterson and Zderad also emphasized the humanistic and existential bases of nursing.

Contemporary nursing theorists addressed the metaparadigm concepts and explored the need for nursing. Myra Levine described four conservation principles for nursing, specifically the conservation of energy, structural integrity, personal integrity, and social stability. According to Levine, people need nursing when they are unable to care for themselves.

Dorothea Orem developed the Self-Care Deficit Theory of Nursing, in which she purports that people need nursing care when they have a “self-care deficit,” or cannot care for themselves. Sister Callista Roy used general systems theory and adaptation theory to produce the Roy Adaptation Model, in which the person is a biopsychosocial being constantly interacting with the environment. The nurse assists the person to adapt a variety of stimuli.

New worldview theorists emphasize the client-environment interaction and caring. Jean Watson developed the theory of Human Caring and described 10 carative factors (nursing actions or processes). Martha Rogers developed the theory of the Science of Unitary Human Beings, in which the person is a unified whole, greater than the sum of the parts. Rosemary Parse, whose ideas were influenced by Martha Rogers, emphasizes understanding the person’s lived experiences as related to health.

Nurses continue to develop theories that work in practice. For example, Gordon’s Functional Health Patterns, an example of middle-range theory, use 11 functional health patterns to provide a framework for assessment, nursing diagnoses, and a plan of care. Nursing theory continues to evolve and change. However, the concept of caring remains the focal point of new theories in nursing.