Immortality is the indefinite continuation of a persons existence, even after death. In common parlance, immortality is virtually indistinguishable from afterlife, but philosophically speaking, they are not identical. Afterlife is the continuation of existence after death, regardless of whether or not that continuation is indefinite. Immortality implies a never-ending existence, regardless of whether or not the body dies (as a matter of fact, some hypothetical medical technologies offer the prospect of a bodily immortality, but not an afterlife).

Immortality has been one of mankinds major concerns, and even though it has been traditionally mainly confined to religious traditions, it is also important to philosophy. Although a wide variety of cultures have believed in some sort of immortality, such beliefs may be reduced to basically three non-exclusive models: (1) the survival of the astral body resembling the physical body; (2) the immortality of the immaterial soul (that is an incorporeal existence); (3) resurrection of the body (or re-embodiment, in case the resurrected person does not keep the same body as at the moment of death). This article examines philosophical arguments for and against the prospect of immortality.

A substantial part of the discussion on immortality touches upon the fundamental question in the philosophy of mind: do souls exist? Dualists believe souls do exist and survive the death of the body; materialists believe mental activity is nothing but cerebral activity and thus death brings the total end of a persons existence. However, some immortalists believe that, even if immortal souls do not exist, immortality may still be achieved through resurrection.

Discussions on immortality are also intimately related to discussions of personal identity because any account of immortality must address how the dead person could be identical to the original person that once lived. Traditionally, philosophers have considered three main criteria for personal identity: the soul criterion , the body criterion and the psychological criterion.

Although empirical science has little to offer here, the field of parapsychology has attempted to offer empirical evidence in favor of an afterlife. More recently, secular futurists envision technologies that may suspend death indefinitely (such as Strategies for Engineered Negligible Senescence, and mind uploading), thus offering a prospect for a sort of bodily immortality.

Discourse on immortality bears a semantic difficulty concerning the word 'death. We usually define it in physiological terms as the cessation of biological functions that make life possible. But, if immortality is the continuation of life even after death, a contradiction appears to come up (Rosemberg, 1998). For apparently it makes no sense to say that someone has died and yet survived death. To be immortal is, precisely, not to suffer death. Thus, whoever dies, stops existing; nobody may exist after death, precisely because death means the end of existence.

For convenience, however, we may agree that death simply means the decomposition of the body, but not necessarily the end of a persons existence, as assumed in most dictionary definitions. In such a manner, a person may die in as much as their body no longer exists (or, to be more precise, no longer holds vital signs: pulse, brain activity, and so forth), but may continue to exist, either in an incorporeal state, with an ethereal body, or with some other physical body.

Some people may think of immortality in vague and general terms, such as the continuity of a persons deeds and memories among their friends and relatives. Thus, baseball player Babe Ruth is immortal in a very vague sense: he is well remembered among his fans. But, philosophically speaking, immortality implies the continuation of personal identity. Babe Ruth may be immortal in the sense that he is well remembered, but unless there is someone that may legitimately claim I am Babe Ruth, we shall presume Babe Ruth no longer exists and hence, is not immortal.

Despite the immense variety of beliefs on immortality, they may be reduced to three basic models: the survival of the astral body, the immaterial soul and resurrection (Flew, 2000). These models are not necessarily mutually exclusive; in fact, most religions have adhered to a combination of them.

Much primitive religious thought conceives that human beings are made up of two body substances: a physical body, susceptible of being touched, smelt, heard and seen; and an astral body made of some sort of mysterious ethereal substance. Unlike the physical body, the astral body has no solidity (it can go through walls, for example.) and hence, it cannot be touched, but it can be seen. Its appearance is similar to the physical body, except perhaps its color tonalities are lighter and its figure is fuzzier.

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Immortality | Internet Encyclopedia of Philosophy