An essential characteristic of APNs is use of theory in practice.70 Clinical nurse specialists (CNSs) use theory to provide or direct patient care, in their work as consultants to staff nurses, and as leaders influencing and facilitating system change.71 Clinical nurse specialists use midrange theories that address phenomena relevant to their specialty. Theory-based practice enhances achievement of positive patient outcomes. It provides an explanation for a person's response to his/her condition or treatment. Theory-based practice helps clinicians be faster as it focuses their assessment. It fosters a match between the theory and evidence-based interventions and outcomes with existing, sensitive measures. Using theory decreases distractions and reduces time obtaining and sorting irrelevant information. It facilitates clear and timely communication with other professionals and interested parties (eg, health plan or insurance). Using theory is smart practice. Clinicians are able to observe patterns more quickly, manage complexity, and provide or direct holistic care. Using theory enhances the development of “practice wisdom” because it fosters pattern recognition.. Using theory helps ensure that a CNS practice is holistic and comprehensive.