Butler (1963) proposes the concept of life review. He defines it as follows:

A naturally occurring, universal mental process characterized by the progressive return to consciousness of past experience, and particularly, the resurgence of unresolved conflicts; simultaneously, and normally, these revived experiences and conflicts can be surveyed and reintegrated . . . prompted by the realization of approaching dissolution and death, and the inability to maintain one's sense of personal invulnerability (p. 66).

This definition of life review process as postulated by Butler (1963) has several characteristics that should be highlighted. First, the process is described as a "naturally occurring, universal mental process". In other words, it is a normal developmental task of old age. As such, the life review process is hypothesized to be experienced by all older adults either consciously or unconsciously.

The life review process is also hypothesized to occur in response to the realization of approaching death. As individuals develop as sense of their own mortality, they come to look back over their lives. This sense of mortality and the concomitant vulnerability that this produces motivates the individual to look back and reassess their life in view of imminent death.

The last prominent feature of Butler's definition is the review process itself. The life review process has often been described as a form of reminiscence (Hausman, 1980). However, for Butler (1963), the life review process and reminiscence are not synonymous. While the life review process may account for greater reminiscence in old age, the process represents more than just a look backward. The life review process is seen as essential to the final reorganization and integration of the personality. Of particular importance to the life review are unresolved conflicts. The life review represents a final opportunity for the individual to resolve and come to understand the conflicts of earlier life. Butler proposes that death can be accepted only through the resolution of conflicts and the resultant personality integration.

There are some features of the life review that are not noted in the definition provided above. Butler (1963) maintains that the life review occurs not only in the elderly but can also occur in the terminally ill or in the condemned. For these individuals, the life review is also prompted by the inevitability of death. In addition, a reminiscence similar to the life review can be seen resulting from introspection and, in particular, introspection in individuals preoccupied with death. Thus, the life review is not the sole property of old age. Rather, old age and the unavoidability of death are inextricably tied together, thus, resulting in the naturally occurring phenomena of the life review in old age. In addition, Butler (1963) maintains that old age is also conducive to the life review process as individuals are becoming disengaged from society and thus, have more time for self-reflection.

The manifestations of the life review can take several forms. First, the process can be silent or oral, conscious or unconscious. This in part depends on the current personality structure of the individual. For some individuals, the process of looking back may be painful. Therefore, only glimpses of the past achieve consciousness with the majority of the review occurring outside the realm of awareness. For example, much of the review may be experienced through dreams. For other individuals, the life review process is experienced much more consciously. Much of the work may take the form of reminiscences that are shared and experienced with significant others. In fact, Butler (1980) maintains that the oral history of the life review has much to offer those individuals with whom the life review experience is shared.

The strength with which the life review is experienced also varies. For some individuals, the life review is experienced only as brief insignificant thoughts. For others, the process may take the form of mild nostalgia or regret. In its severe form, it can be experienced as anxiety, guilt, and/or depression. The severity of the life review is in part due to the outcome of the review. According to Butler (11963), as individuals realize that there is limited time remaining to them, they will examine what kind of life they have lived. They may examine whether they feel their life was a success or failure. They may look at what kind of person they feel they have become. If this review results in a positive evaluation, then the individual is thought to be able to deal with death positively. If the review results in a negative evaluation, the person may fall into despair. In other words, the person may be filled with regrets and want to change his/her life but may not feel they have enough time, thus making the prospect of death difficult to endure. Butler (1963) maintains that the outcome of the process is primarily influenced by the function of the personality as opposed to environmental influences.

The life review process is postulated to have the therapeutic outcome for those individuals who assess their life to be a success. Two positive outcomes are conceptualized to result from the outcome of a successful life review. First, the personality is hypothesized to reorganize into a more integrated whole. As such, it is similar to the process of individuation as described by Jung (1959). Second, the life review is seen as a preparation for death. As the individual is able to accept their life, they are thus hypothesized to accept their death. This acceptance is proposed to eliminate or mitigate a fear of death. As such Butler (1963) maintains that his may account for the wisdom and serenity that one often observes in the older adult.

For those individuals who assess their life to be a failure, the life review process is hypothesized to produce psychopathological manifestations (Butler, 1963). These manifestations may take the form of guilt, depression, and anxiety. It its extreme form, Butler (1963) states, "it may involve the obsessive preoccupation of the older person in his past and may proceed to a state approximating terror and result in suicide" (p. 269).

Butler (1963) proposes that three groups are at significant risk for psychopathological outcomes as a result of life review. The first group that Butler describes as being at risk are individuals who always look to the future and avoid the past or present. For these individuals, the future holds promise and achievement. The future is a way to avoid current and past conflict. However, as these individuals age, the future may not be able to deliver on its promises. Rather, the future holds the inevitability of death.

The second group at risk for pathological guilt, depression, or anxiety are those individuals who at some point in their life have severely and consciously injured others. For these individuals, guilt is real. There is no way to reverse the injury. Therefore, these individuals often can see no way to achieve a positive life review outcome.

The narcissistic individual represents the third group at risk for psychopathological manifestations resulting from the life review process. Butler (1963) hypothesizes that the threat of death presents an insurmountable threat to their narcissism. Therefore, the life review for the prideful and arrogant may result in extreme depression.

In addition to the life review as a normal developmental task, Butler (1980) argues for its use as a therapeutic tool. Butler (1980) proposes three reasons why the life review might be termed "an unrecognized bonanza" (p.35). First, Butler argues the process of reminiscence often has a therapeutic benefit. It affords the individual the opportunity to talk about their past and their past conflicts. This provides the individual an environment conducive to the integration, reorganization, and resolution of past experiences. Butler maintains that the use of the life review is conducive not only to individual therapy, but also group and family therapy.

Second, Butler (1980) maintains that slips of the tongue often occur during the process of an oral history or life review reminiscence. These slips of the tongue provide valuable information to be used in the therapeutic setting.

The third reason that Butler (1980) proposes that the life review is valuable is as a tool with which older adults can leave a legacy. The desire to leave a legacy has been identified by Traxler (1980) as another developmental task of later adulthood. Butler maintains that the recording or transcription of on individual's oral history can provide such a legacy. Butler states, "There is perhaps no other group that can tell us something about the nature of human life with all of its successes and problems better than old people" (p. 37). Thus, the oral history can provide a means by which older adults can make their mark on succeeding generations.