Immortality is a continuation of a person’s infinite existence, even after death. In common parlance, eternity is actually indistinguishable from life after death, but philosophically, they are not identical. The afterlife is a continuation of existence after death, regardless of whether the continuation is unlimited or not.

Immortality implies a never-ending existence, regardless of whether the body dies or not, as a matter of fact, some hypothetical medical technology offers the prospect of bodily immortality, but not life after death.

Eternity has become one of the main concerns of humanity, and although traditionally limited to religious traditions, it is also important for philosophy. Although various cultures have believed in a kind of eternity, such beliefs can basically be reduced to three non-exclusive models:

1. The survival of the astral body resembles the physical body;
2. Immortality of the immaterial soul (ie incorporeal existence);
3. The resurrection of the body or re-manifestation, in the case of the resurrected person, does not maintain the same body as at the time of death.

This article discusses philosophical arguments for and opposes the prospect of eternity.

Most discussions of eternity touch upon a fundamental question in the philosophy of mind: is there a soul? Dualists believe that the soul does exist and survives the death of the body; materialists believe mental activity is nothing but brain activity and thus death brings an end to the total existence of a person. However, some immortals believe that, even if immortal souls do not exist, eternity can still be achieved through resurrection.

The discussion on eternity is also closely related to the discussion on personal identity because each eternity account must discuss how a dead person can be identical to a native person who has ever lived. Traditionally, philosophers have considered three main criteria for personal identity: soul criteria, body criteria and psychological criteria.

Although empirical science has little to offer here, the field of parapsychology has sought to offer empirical evidence in support of life after death. More recently, secular futurists have imagined technologies that can suspend death indefinitely, such as Strategies for Ignored Engineations that Can Be Engineered, and upload minds, thus offering the prospect of a kind of immortality of the body.

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Semantic Problems

The discourse about eternity brings semantic difficulties regarding the word ‘death’. We usually define it in physiological terms as the termination of the biological functions that make life possible. However, if eternity is a continuation of life even after death, a contradiction arises. Because it seems absurd to say that someone has died and survived death. Being immortal, precisely, is not to suffer death.

So whoever dies, stops there; no one can exist after death, precisely because death means the end of existence.

For convenience, however, we can agree that ‘death’ means decomposition of the body, but not necessarily the end of one’s existence, as assumed in most dictionary definitions. In such a way, a person can ‘die’ as much as their body no longer exists (or, more precisely, no longer holds vital signs: pulse, brain activity, etc.), but can continue to exist, both in the incorporeal state, with the body smooth, or with other physical bodies.

Some people might think of ‘eternity’ in vague and general terms, such as the continuation of one’s actions and memories between their friends and relatives. As such, baseball player Babe Ruth is immortal in a very vague sense: he is well remembered among his fans. But, philosophically, eternity implies a continuation of personal identity. Babe Ruth may be immortal in the sense that she is well remembered, but unless someone legitimately claims “I am Babe Ruth,” we will assume Babe Ruth no longer exists and, therefore, is not eternal.

Three Eternity Models

Apart from the diversity of beliefs about eternity, they can be reduced to three basic models: the survival of the astral body, immaterial soul, and resurrection. These models do not have to be mutually exclusive; in fact, most religions adhere to a combination of both.

1. Survival of the Astral Body

Much primitive religious thought understands that humans consist of two body substances: the physical body, vulnerable to being touched, kissed, heard and seen; and an astral body made of some kind of mysterious subtle object. Unlike the physical body, the astral body has no solidity, it can penetrate walls, for example. And hence, he cannot be touched, but he can be seen. His appearance is similar to the physical body, except maybe his color tone is lighter and his figure is fuzzier.

After death, the astral body detaches from the physical body and grieves in several regions in time and space. So, even if the physical body decays, the astral body survives.

This is the most common type of eternity presented in film and literature (for example, Hamlet’s ghost). Traditionally, philosophers and theologians have not privileged this model of eternity, because there seem to be two insurmountable difficulties:

if the astral body exists, it must be seen to deviate from the physical body at the time of death; but there is no evidence to explain it;
ghosts usually appear with clothes; this would imply that there are not only astral bodies, but also astral clothing.

2. The immaterial soul

The model of the immortality of the soul is similar to the ‘astral body’ model, in many ways assuming that humans consist of two substances. However, unlike the ‘astral body’ model, this model understands that the substance that survives the death of the body is not another type of body, but rather, the insignificant material of the soul. It has no extension, and as such, it cannot be felt through the senses. Some philosophers, such as Henry James, have believed that for something to exist, it must occupy space (although it does not have to be physical space), and therefore, the soul is somewhere in space (Henry, 2007).

Until the twentieth century, the majority of philosophers believed that humans were souls and that humans consisted of two substances (soul and body). Most philosophers believe that this body is mortal and the soul is eternal. Since Descartes in the seventeenth century, most philosophers have assumed that the soul is identical with the mind, and, every time someone dies, their mental content remains in an intangible state.

Hindu and Buddhist religions and some ancient philosophers Pythagoras and Plato believe that immortal souls leave the body at the time of death, can live temporarily in an incorporeal state, and can eventually be attached to a new body at birth (in some traditions, at the time of conception). This is the doctrine of reincarnation.

3. Awakening of the Body

While most Greek philosophers believe that eternity implies solely the survival of the soul, the three major monotheistic religions of Judaism, Christianity and Islam assume that eternity is achieved through the resurrection of the body at the Last Judgment. The same body that people have formed will rise again, to be judged by God. None of these great beliefs have a definite position about the existence of an eternal soul. Therefore, traditionally, Jews, Christians and Muslims believe that, at the time of death, the soul is detached from the body and continues to live in an intermediate incorporeal state until the resurrection. However, some others believe that there is no transitional state: with death, that person no longer exists, and in a sense, continues his existence at the time of the resurrection.

As we will see, some philosophers and theologians have postulated the possibility that, after the resurrection, people do not rise with the same bodies they once lived (but rather, those raised will be formed by replicas). This version of the doctrine of resurrection would be better referred to as ‘re-manifestation’: the person dies, but, as if, ‘re-manifested’.