Nursing assessment utilizes skills that enable the nurse to "sense" the patient's needs and the patient's condition, and that provide a humanistic dimension to the provision of nursing care. The explanatory concepts describing these processes include intuition, emotional empathy, inference, knowing, counter transference, compathy and embodiment. In this paper these concepts are defined, and the more commonly used concepts (i.e., intuition, empathy, and inference) are compared. The underlying assumptions and characteristics are identified and the antecedents or prerequisites, mechanisms, and outcomes of each concept are explored. While some overlap and blurring of boundaries are evident, these concepts are diverse and were developed to apply to different contexts and non-nursing situations. When used alone, none is comprehensive enough to account for nurses' ability to sense patient needs. We conclude that, given the unique aspects of nursing, we must consider using innovative methods to examine this phenomenon (e.g., the use of ethology to examine intuitively perceived changes in the patient's condition), to increase efforts to explore the newer concepts (i.e., embodiment, compathy and "knowing"), and to develop new concepts or models that better represent this complex phenomenon that better fits nursing contexts and situations.