Nursing theory is defined as "a creative and rigorous structuring of ideas that project a tentative, purposeful, and systematic view of phenomena". Through systematic inquiry, whether in nursing research or practice, nurses are able to develop knowledge relevant to improving the care of patients. Theory refers to "a coherent group of general propositions used as principles of explanation". Nursing theory Importance In the early part of nursing's history, there was little formal nursing knowledge. As nursing education developed, the need to categorize knowledge led to development of nursing theory to help nurses evaluate increasingly complex client care situations. Nursing theories give a plan for reflection in which to examine a certain direction in where the plan needs to head. As new situations are encountered, this framework provides an arrangement for management, investigation and decision-making. Nursing theories also administer a structure for communicating with other nurses and with other representatives and members of the health care team. Nursing theories assist the development of nursing in formulating beliefs, values and goals. They help to define the different particular contribution of nursing with the care of clients. Nursing theory guides research and practice. Borrowed and shared theories Not all theories in nursing are unique nursing theories; many are borrowed or shared with other disciplines. Theories developed by Neuman, Watson, Parse, Orlando and Peplau are considered unique nursing theories. Theories and concepts that originated in related sciences have been borrowed by nurses to explain and explore phenomena specific to nursing. Types Grand nursing theories Grand nursing theories have the broadest scope and present general concepts and propositions. Theories at this level may both reflect and provide insights useful for practice but are not designed for empirical testing. This limits the use of grand nursing theories for directing, explaining, and predicting nursing in particular situations. However, these theories may contain concepts that can lend themselves to empirical testing. Theories at this level are intended to be pertinent to all instances of nursing. Grand theories consist of conceptual frameworks defining broad perspectives for practice and ways of looking at nursing phenomena based on the perspectives. Mid-range nursing theories Middle-range nursing theories are narrower in scope than grand nursing theories and offer an effective bridge between grand nursing theories and nursing practice. They present concepts and a lower level of abstraction and guide theory-based research and nursing practice strategies. One of the hallmarks of mid-range theory compared