The term aloneness may be understood in many different ways. In the simplest case, other people are physically absent. Despite this state of affairs, not everyone will experience a sense of aloneness, especially if other people are imagined or if the person has no desire to be with them at that moment. Similarly, a person may be surrounded by other people and still experience an uncomfortable sense of being alone, particularly if he or she feels excluded from participating with them in a meaningful way. Aloneness does not refer to an objective circumstance but to a psychological mode of being, and whether it is experienced as pleasurable or painful, problematic or liberating, always depends upon the meaning that each specific situation has for the person undergoing it.

Being alone is not only a common human condition but one so close to what human existence is about as to be inevitable and unavoidable. As Paul Tillich (1963) noted:

In examining prior work on aloneness, four major perspectives can be discerned: psychodynamic, sociological, existential, and phenomenological. From a psychodynamic perspective, aloneness is frequently characterized as a condition of the person, and sources of aloneness are sought both in the intrapsychic world and in the developmental history of the individual.