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Economist, July 2010: Why do we grow old? And is ageing really compulsory? 

"FOR as long as people have been growing old, they’ve been wishing they didn’t have to. The “Epic of Gilgamesh”, one of the most ancient works of literature, chronicles the eponymous hero’s quest for eternal life. Most religions offer an attenuated version of immortality in which some fuzzily defined soul endures even after the body has died. Medieval alchemists hunted in vain for the rejuvenating Philosopher’s Stone; industrial-age quacks got rich off their patent elixirs. Today, cosmetics companies dance around truth-in-advertising laws to imply that their creams and lotions can keep the years at bay.

Yet for all the gloomy fascination that surrounds ageing, precious little research has been done into its causes. The question of why we grow old and die still divides evolutionary biologists. Strictly speaking, ageing does not seem to be inevitable. After all, both cancer cells and some very simple forms of life appear highly resistant to the passage of time. And while we know plenty about the consequences of ageing, we know much less about the exact biological processes involved. The little interest shown was until recently limited to quacks and cranks, leavened with the occasional iconoclastic scientist (such as Peter Medawar, a brilliant British zoologist) with a reputation strong enough to survive developing an interest in a thoroughly disreputable field.

In the past couple of decades that has begun to change. Improvements in technology, particularly the ability to sequence DNA quickly, have made the serious study of ageing possible. [...] Plenty of progress has already been made. Genes have been found that boost the lifespans of laboratory animals by 30% or more, and research into the mechanisms of ageing has fingered some tantalising leads: ageing seems to be associated with a low-level, chronic inflammation of many of the body’s tissues, for instance. Insulin, a hormone that regulates the metabolism of glucose, also crops up.

Most intriguing of all is something that scientists have known for decades: feeding near-starvation diets to laboratory animals such as mice and fruit flies can extend their lifespans by 40% or more, and improve health along the way. If those results translated directly to humans (and there is some preliminary evidence that fasting may confer benefits in people), then the human lifespan could reach 150 years. Many explanations have been offered and discarded to explain the power of dieting: that it reduces production of the harmful chemicals that are a side-effect of respiration, for instance, or that it lowers blood-sugar levels, which seems to have a variety of health benefits. Proponents of this theory are searching for drugs, so-called “calorie-restriction mimetics”, that can produce these effects without requiring aspiring centenarians to endure 100 years of non-stop dieting. Several firms have been set up to capitalise on the findings, in the hope of developing and selling pills that grant longer, healthier lives
." For more, read:

As immortality is the negation of mortality—not dying or not being subject to death—it has been a subject of fascination to humanity since at least the beginning of known history.  What form an unending human life would take (as well as whether it is subject to incapacitation), or whether the soul exists and possesses immortality, has been a major point of focus of religion, as well as the subject of speculation, fantasy, and debate.

It is not known whether human physical immortality is an achievable condition. Biological forms have inherent limitations which may or may not be able to be overcome through medical interventions or engineering. As of 2009, natural selection has developed biological immortality in at least one species, the jellyfish Turritopsis nutricula, one consequence of which is a worldwide population explosion of the organism.

Certain scientists, futurists, and philosophers, such as Ray Kurzweil, advocate that human immortality is achievable in the first few decades of the 21st century, while other advocates believe that life extension is a more achievable goal in the short term, with immortality awaiting further research breakthroughs further into an indefinite future. Aubrey de Grey, a researcher who has developed a series of biomedical rejuvenation strategies to reverse human aging (called SENS), believes that his proposed plan for ending aging may be implementable in two or three decades. The absence of aging would provide humans with biological immortality, but not invulnerability to death by physical trauma.

Eternal life can also be defined as a timeless existence, which is also not known for certain to be achievable, or even definable, despite millennia of arguments for eternity. Wittgenstein, in a notably non-theological interpretation of eternal life, writes in the Tractatus that, "If we take eternity to mean not infinite temporal duration but timelessness, then eternal life belongs to those who live in the present." 

The belief in an afterlife is a fundamental tenet of religions, including Hinduism, Sikhism, Christianity, Zoroastrianism, Islam, Judaism, and the Bahá'í Faith. However the concept of an immortal soul is not,.The 'soul' itself has different meanings and is not used in the same way in different religions and different sects of a religion.

Fame itself has been described as a method to "achieve immortality", if only semantically, so that the name or works of a famous individual would "live on" after his or her death. This view of immortality places value on how one will be remembered by generations to come. For example, in Homer's Iliad, Achilles is already nigh-invincible, so his primary motive for fighting in the Trojan War is recognition and everlasting fame.
Mystic approaches to immortality include those of the ancient Chinese Taoists and European medieval alchemists, seeking an elixir of life.
Should metaphysical universals and abstract phenomena have an eternal existence, and if they can be interacted with by human beings, then a person might obtain a degree of immortality by interacting with them.

Quantum immortality is not widely regarded by the scientific community as being a verifiable or even necessarily correct offshoot of the many worlds interpretation. In the many worlds interpretation of quantum mechanics, the wavefunction never collapses, and thus all possible outcomes of a quantum event exist simultaneously, with each event apparently spawning an entirely new universe in which a single possible outcome exists. In this theory, a person could hypothetically live forever as there might exist a string of possible quantum outcomes in which that individual never dies. 

The persistence of life itself across time is a form of immortality, insofar as leaving surviving offspring or genetic material is a means of defeating death.
Life extension technologies promise a path to complete rejuvenation. Cryonics holds out the hope that the dead can be revived in the future, following sufficient medical advancements.
Mind uploading is the concept of transference of consciousness from a human brain to an alternative medium providing the same functionality. Assuming the process to be possible and repeatable, this would provide immortality to the consciousness, as predicted by futurists such as Ray Kurzweil.
[edit] Physical immortality
Physical immortality is a state of life that allows a person to avoid death and maintain conscious thought. It can mean the unending existence of a person from a physical source other than organic life, such as a computer. In the early 21st century, physical immortality remains a goal rather than a current reality. Active pursuit of physical immortality can either be based on scientific trends, such as cryonics, digital immortality, breakthroughs in rejuvenation or predictions of an impending technological singularity, or because of a spiritual belief, such as those held by Rastafarians or Rebirthers.

Causes of death
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By definition, all causes of death must be overcome or avoided for physical immortality to be achieved. There are three main causes of death: aging, disease and trauma. 

Aubrey de Grey, a leading researcher in the field, defines aging as follows: "a collection of cumulative changes to the molecular and cellular structure of an adult organism, which result in essential metabolic processes, but which also, once they progress far enough, increasingly disrupt metabolism, resulting in pathology and death." The current causes of aging in humans are cell loss (without replacement), oncogenic nuclear mutations and epimutations, cell senescence, mitochondrial mutations, lysosomal aggregates, extracellular aggregates, random extracellular cross-linking, immune system decline, and endocrine changes. Eliminating aging would require finding a solution to each of these causes, a program de Grey calls engineered negligible senescence.[6][10] 

Disease is theoretically surmountable via technology. Human understanding of genetics is leading to cures and treatments for a myriad of previously incurable diseases. The mechanisms by which other diseases do their damage are becoming better understood. Sophisticated methods of detecting diseases early are being developed. Preventative medicine is becoming better understood. Neurodegenerative diseases like Parkinson's and Alzheimer's may soon be curable with the use of stem cells. Breakthroughs in cell biology and telomere research are leading to treatments for cancer. Vaccines are being researched for AIDS and tuberculosis. Genes associated with type 1 diabetes and certain types of cancer have been discovered allowing for new therapies to be developed. Artificial devices attached directly to the nervous system may restore sight to the blind. Drugs are being developed to treat myriad other diseases and ailments. 

Physical trauma would remain as a threat to perpetual physical life, even if the problems of aging and disease were overcome, as an otherwise immortal person would still be subject to unforeseen accidents or catastrophes. Ideally, any methods to achieve physical immortality would mitigate the risk of encountering trauma. Taking preventative measures by engineering inherent resistance to injury is thus relevant in addition to entirely reactive measures more closely associated with the paradigm of medical treatment.[citation needed]

The speed and quality of paramedic response remains a determining factor in surviving severe trauma. A body that could automatically treat itself from severe trauma, such as speculated uses for nanotechnology, would mitigate this factor. Without improvements to such things, very few people would remain alive after several tens of thousands of years purely based on accident rate statistics, much less millions or billions or more.

Being the seat of consciousness, the brain cannot be risked to trauma if a continuous physical life is to be maintained. Therefore, it cannot be replaced or repaired in the same way other organs can. A method of transferring consciousness would be required for an individual to survive trauma to the brain, and this transfer would have to anticipate and precede the damage itself.[citation needed]

There is no logical or mathematical limitation on the degree of gradual mitigation of risk over time, so although there would be an expectation greater than zero of eventual death it cannot be proven that death even by unforeseen events causing trauma would be absolutely assured for any specific or even any single remaining person. 

Biological immortality

Human chromosomes (grey) capped by telomeres (white)Main article: Biological immortality
Biological immortality is an absence of aging, specifically the absence of a sustained increase in rate of mortality as a function of chronological age. A cell or organism that does not experience aging, or ceases to age at some point, is biologically immortal.

Biologists have chosen the word immortal to designate cells that are not limited by the Hayflick limit, where cells no longer divide because of DNA damage or shortened telomeres. Prior to the work of Leonard Hayflick there was the erroneous belief fostered by Alexis Carrel that all normal somatic cells are immortal. By preventing cells from reaching senescence one can achieve biological immortality; telomeres, a "cap" at the end of DNA, are thought to be the cause of cell aging. Every time a cell divides the telomere becomes a bit shorter; when it is finally worn down, the cell is unable to split and dies. Telomerase is an enzyme which rebuilds the telomeres in stem cells and cancer cells, allowing them to replicate an infinite number of times. No definitive work has yet demonstrated that telomerase can be used in human somatic cells to prevent healthy tissues from aging. On the other hand, scientists hope to be able to grow organs with the help of stem cells, allowing organ transplants without the risk of rejection, another step in extending human life expectancy. These technologies are the subject of ongoing research, and are not yet realized. 

Biologically immortal species
Life defined as biologically immortal is still susceptible to causes of death besides aging, including disease and trauma, as defined above. Notable immortal species include:

Turritopsis nutricula, a jellyfish, after becoming a sexually mature adult, can transform itself back into a child (the polyp stage) using the cell conversion process of transdifferentiation. Turritopsis nutricula repeats this cycle, meaning that it may have an indefinite lifespan. Its immortal adaptation has allowed it to spread from its original habitat in the Caribbean to "all over the world".
Bacteria (as a colony) — Bacteria reproduce through cell division. A parent bacterium splits itself into two identical daughter cells. These daughter cells then split themselves in half. This process repeats, thus making the bacterium colony essentially immortal.
Recent research, however, suggests that even bacteria as a colony may eventually die since each succeeding generation is slightly smaller, weaker, and more likely to die than the previous.
Hydra can be considered biologically immortal as they do not undergo senescence or aging.
Bristlecone Pines are speculated to be potentially immortal; the oldest known living specimen is over 4800 years old.
[edit] Evolution of aging

Evolution of aging
As the existence of biologically immortal species demonstrates, there is no thermodynamic necessity for senescence: a defining feature of life is that it takes in free energy from the environment and unloads its entropy as waste. Living systems can even build themselves up from seed, and routinely repair themselves. Aging is therefore presumed to be a byproduct of evolution, but why mortality should be selected for remains a subject of research and debate. Programmed cell death and the telomer "end replication problem" are found even in the earliest and simplest of organisms. This may be a tradeoff between selecting for cancer and selecting for aging.

Modern theories on the evolution of aging include the following:

Mutation accumulation is a theory formulated by Peter Medawar in 1952 to explain how evolution would select for aging. Essentially, aging is never selected against, as organisms have offspring before the mortal mutations surface in an individual.
Antagonistic pleiotropy is a theory proposed as an alternative by George C. Williams, a critic of Medawar, in 1957. In antagonistic pleiotropy, genes carry effects that are both beneficial and detrimental. In essence this refers to genes that offer benefits early in life, but exact a cost later on, i.e. decline and death.[17]
The disposable soma theory was proposed in 1977 by Thomas Kirkwood, which states that an individual body must allocate energy for metabolism, reproduction, and maintenance, and must compromise when there is food scarcity. Compromise in allocating energy to the repair function is what causes the body gradually to deteriorate with age, according to Kirkwood.

Prospects for human biological immortality
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Life-extending substances
There are some known naturally occurring and artificially produced chemicals that can dramatically increase the lifetime or life-expectancy of a person or organism, such as resveratrol. Future research might enable scientists to increase the effect of these existing chemicals or to discover new chemicals (life-extenders) which might enable a person to stay alive as long as the person consumes them at specified periods of time.

Scientists believe that boosting the amount or proportion of a naturally forming enzyme, telomerase, in the body could prevent cells from dying and so may ultimately lead to extended, healthier lifespans. Telomerase is a protein that helps maintain the protective caps at the ends of chromosomes. A team of researchers at the Spanish National Cancer Centre (Madrid) tested the hypothesis on mice. It was found that those mice which were genetically engineered to produce 10 times the normal levels of telomerase lived 50% longer than normal mice.

In normal circumstances, without the presence of telomerase, if a cell divides recursively, at some point all the progeny will reach their Hayflick limit. With the presence of telomerase, each dividing cell can replace the lost bit of DNA, and any single cell can then divide unbounded. While this unbounded growth property has excited many researchers, caution is warranted in exploiting this property, as exactly this same unbounded growth is a crucial step in enabling cancerous growth.

Embryonic stem cells express telomerase, which allows them to divide repeatedly and form the individual. In adults, telomerase is highly expressed in cells that need to divide regularly (e.g., in the immune system), whereas most somatic cells express it only at very low levels in a cell-cycle dependent manner. 

Technological immortality 
Technological immortality is the prospect for much longer life spans made possible by scientific advances in a variety of fields: nanotechnology, emergency room procedures, genetics, biological engineering, regenerative medicine, microbiology, and others. Contemporary life spans in the advanced industrial societies are already markedly longer than those of the past because of better nutrition, availability of health care, standard of living and bio-medical scientific advances. Technological immortality predicts further progress for the same reasons over the near term. An important aspect of current scientific thinking about immortality is that some combination of human cloning, cryonics or nanotechnology will play an essential role in extreme life extension. Robert Freitas, a nanorobotics theorist, suggests tiny medical nanorobots could be created to go through human bloodstreams, find dangerous things like cancer cells and bacteria, and destroy them. Freitas anticipates that gene-therapies and nanotechnology will eventually make the human body effectively self-sustainable and capable of living indefinitely, short of severe brain trauma. This supports the theory that we will be able to continually create biological or synthetic replacement parts to replace damaged or dying ones. 

Cryonics, the practice of preserving organisms (either intact specimens or only their brains) for possible future revival by storing them at cryogenic temperatures where metabolism and decay are almost completely stopped, is the answer for those who believe that life extension technologies like nanotechnology or nanorobots will not develop sufficiently within their lifetime. Ideally, cryonics would allow clinically dead people to be brought back in the future after cures to the patients' diseases have been discovered and aging is reversible. Modern cryonics procedures use a process called vitrification which creates a glass-like state rather than freezing as the body is brought to low temperatures. This process reduces the risk of ice crystals damaging the cell-structure, which would be especially detrimental to cell structures in the brain, as their minute adjustment evokes the individual's mind. 

Mind-to-computer uploading
One idea that has been advanced involves uploading an individual's personality and memories via direct mind-computer interface.The individual's memory may be loaded to a computer or to a newly born baby's mind. The baby will then grow with the previous person's individuality, and may not develop its own personality. Extropian futurists like Moravec and Kurzweil have proposed that, thanks to exponentially growing computing power, it will someday be possible to upload human consciousness onto a computer system, and live indefinitely in a virtual environment. This could be accomplished via advanced cybernetics, where computer hardware would initially be installed in the brain to help sort memory or accelerate thought processes. Components would be added gradually until the person's entire brain functions were handled by artificial devices, avoiding sharp transitions that would lead to issues of identity. After this point, the human body could be treated as an optional accessory and the mind could be transferred to any sufficiently powerful computer. Another possible mechanism for mind upload is to perform a detailed scan of an individual's original, organic brain and simulate the entire structure in a computer. What level of detail such scans and simulations would need to achieve to emulate consciousness, and whether the scanning process would destroy the brain, is still to be determined.[24] Whatever the route to mind upload, persons in this state would then be essentially immortal, short of loss or traumatic destruction of the machines that maintained them.

Joseph Wright of Derby, The Alchymist, In Search of the Philosopher's Stone, 1771 Mystical and religious pursuits of physical immortality
Many Indian fables and tales include instances of metempsychosis — the ability to jump into another body — performed by advanced Yogis in order to live a longer life. There are also entire Hindu sects devoted to the attainment of physical immortality by various methods, namely the Naths and the Aghoras.[citation needed]

Long before modern science made such speculation feasible, people wishing to escape death turned to the supernatural world for answers. Examples include Chinese Taoists[citation needed] and the medieval alchemists and their search for the Philosopher's Stone, or more modern religious mystics, who believed in the possibility of achieving physical immortality through spiritual transformation.

Individuals claiming to be physically immortal include Comte de Saint-Germain; in 18th century France, he claimed to be centuries old, and people who adhere to the Ascended Master Teachings are convinced of his physical immortality. An Indian saint known as Vallalar claimed to have achieved immortality before disappearing forever from a locked room in 1874.

Rastafarians believe in physical immortality as a part of their religious doctrines. They believe that after God has called the Day of Judgment they will go to what they describe as Mount Zion in Africa to live in freedom for ever. They avoid the term "everlasting life"' and deliberately use "ever-living" instead.

Another group that believes in physical immortality are the Rebirthers, who believe that by following the connected breathing process of rebirthing they can physically live forever.

Religious traditions
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Until the late 20th century, there were no creditable scientific forecasts that physical immortality was obtainable. As late as 1952, the editorial staff of the Syntopicon found in their compilation of the Great Books of the Western World, that "The philosophical issue concerning immortality cannot be separated from issues concerning the existence and nature of man's soul."[26] Thus, the vast majority of speculation regarding immortality before the 21st century was regarding the nature of the afterlife.

Spiritual immortality is the unending existence of a person from a nonphysical source, or in a nonphysical state, such as a soul. Specifically 'soul immortality' is a belief that is expressed in nearly every religious tradition. However any doctrine in this area misleads without a prior definition of 'soul'. Another problem is that 'soul' is often confused and used synonymously or interchangeably with 'spirit'.

In both Western and Eastern religions, the spirit is an energy or force that transcends the mortal body, and returns to: (1) the spirit realm whether to enjoy heavenly bliss or suffer eternal torment in hell, or; (2) the cycle of life, directly or indirectly depending on the tradition.

The world's major religions hold a number of perspectives on spiritual immortality. 

Buddhism teaches that there is a cycle of birth, death, and rebirth and that the process is according to the qualities of a person's actions. This constant process of becoming ceases at the fruition of Bodhi (enlightenment) at which a being is no longer subject to causation (karma) but enters into a state that the Buddha called amata (deathlessness).

According to the philosophical premise of the Buddha, the initiate to Buddhism who is to be "shown the way to Immortality (amata)",[27] wherein liberation of the mind (cittavimutta) is effectuated through the expansion of wisdom and the meditative practices of sati and samādhi, must first be educated away from his former ignorance-based (avijja) materialistic proclivities in that he "saw any of these forms, feelings, or this body, to be my Self, to be that which I am by nature".

Thus, desiring a soul or ego (ātman) to be permanent is a prime consequence of ignorance, itself the cause of all misery and the foundation of the cycle of reincarnation (saṃsāra). Form and consciousness being two of the five skandhas, or aggregates of ignorance, Buddhism teaches that physical immortality is neither a path to enlightenment, nor an attainable goal: even the gods which can live for eons eventually die. Upon enlightenment, the "karmic seeds" (saṅkhāras or sanskaras) for all future becoming and rebirth are exhausted. After biological death an arhat, or buddha, enters into parinirvana, an everlasting state of transcendental happiness. 

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Representation of a soul undergoing punarjanma. Illustration from Hinduism Today, 2004Hindus believe in an immortal soul which is reincarnated after death. According to Hinduism, people repeat a process of life, death, and rebirth in a cycle called samsara. If they live their life well, their karma improves and their station in the next life will be higher, and conversely lower if they live their life poorly. Eventually after many life times of perfecting its karma, the soul is freed from the cycle and lives in perpetual bliss. There is no eternal torment in Hinduism, temporal existence being harsh enough, although if a soul consistently lives very evil lives, it could work its way down to the very bottom of the cycle. Punarjanma means the birth of a person that pays for all the karma of previous lives in this birth.

Sri Aurobindo states that the Vedic and the post-Vedic rishis (such as Markandeya) attained physical immortality, which includes the ability to change one's shape at will, and create multiple bodies simultaneously in different locations.

The Aghoris of India consume human flesh in pursuit of immortality and supernatural powers,they call themselves gods and according to them they punish the sinners by rewarding them death on their way to immortality.  They distinguish themselves from other Hindu sects and priests by their alcoholic and cannibalistic rituals.

Another view of immortality is traced to the Vedic tradition by the interpretation of Maharishi Mahesh Yogi:

That man indeed whom these (contacts)
do not disturb, who is even-minded in
pleasure and pain, steadfast, he is fit
for immortality, O best of men.

To Maharishi Mahesh Yogi, the verse means, "Once a man has become established in the understanding of the permanent reality of life, his mind rises above the influence of pleasure and pain. Such an unshakable man passes beyond the influence of death and in the permanent phase of life: he attains eternal life… A man established in the understanding of the unlimited abundance of absolute existence is naturally free from existence of the relative order. This is what gives him the status of immortal life." 

Taoist beliefs by Xiu Xing and Lian Dan, include that one can achieve immortality to become an enlightened person, or Xian.

Henri Maspero noted that many scholarly works frame Taoism as a school of thought focused on the quest for immortality. Isabelle Robinet asserts that Taoism is better understood as a way of life than as a religion, and that its adherents do not approach or view Taoism the way non-Taoist historians have done.[32] 

Shintoists claim that except for those who choose or are dispatched to the underground world of Yomi, every living and non-living being may lose its body, but not its soul (tamashii), and that they live together with mortal souls as an immortal being called Kami. Shinto allows anything to attain Kami status regardless of its existence before becoming Kami. Therefore, even those that do not believe in Shinto may choose to become Kami, as well as things like a rock, or a tree. Some may be reincarnated for various reasons. 

Zoroastrians believe that on the fourth day after death, the human soul leaves the body and the body remains as an empty shell. Souls would go to either heaven or hell; these concepts of the afterlife in Zoroastrianism may have influenced Abrahamic religions. Word "Immortal" is driven from The month in Iranian calendar "Amurdad" (Near end of July)in Persian meaning "Deathless" Month of Amurdad or Amertata is celebrated in Persian Culture as their Ancestors believed in this month Angel of Immortality win over Angel of death. 

Ancient Greek Religion
In ancient Greek religion immortality originally always included an eternal union of body and soul. The soul was considered to have an eternal existence in Hades, but without the body the soul was considered dead. Although almost everybody had nothing to look forward to but an eternal existence as a disembodied dead soul, a number of men and women were considered to have gained physical immortality and brought to live forever in either Elysium, the Islands of the Blessed, heaven, the ocean or literally right under the ground. Among these were Amphiaraus Ganymede, Ino, Iphigenia Menelaus, Peleus, and a great part of those who fought in the Trojan and Theban wars. Some were considered to have died and been resurrected before they achieved physical immortality. Asclepius, was killed by Zeus only to be resurrected and transformed into a major deity. Achilles after being killed was snatched from his funeral pyre by his divine mother Thetis and resurrected brought to an immortal existence in either Leuce, Elysian plains or the Islands of the Blessed. Memnon, who was killed by Achilles, seems to have a received a similar fate. Alcmene, Castor, Heracles, and Melicertes, were also among the figures sometimes considered to have been resurrected to physical immortality. According to Herodotus' Histories, the seventh century B.C. sage Aristeas of Proconnesus, was first found dead, after which his body disappeared from a locked room. Later he found not only to have been resurrected but to have gained immortality.

The philosophical idea of an immortal soul was a later invention, which, although influential, never had a breakthrough in the Greek world. As may be witnessed even into the Christian era, not least by the complaints of various philosophers over popular beliefs, traditional Greek believers maintained the conviction that certain individuals were resurrected from the dead and made physically immortal and that for the rest of us, we could only look forward to an existence as disembodied and dead souls.

The parallel between these traditional beliefs and the later resurrection of Jesus was not lost on the early Christians, as Justin Martyr argued: "when we say … Jesus Christ, our teacher, was crucified and died, and rose again, and ascended into heaven, we propose nothing different from what you believe regarding those whom you consider sons of Zeus." (1 Apol. 21). 

In both Judaism and Christianity, there is no biblical support of 'soul immortality' as such. The focus is on attaining resurrection life after death on the part of the believers.

Judaism claims that the righteous dead will be resurrected in the Messianic age with the coming of the messiah. They will then be granted immortality in a perfect world. The wicked dead, on the other hand, will not be resurrected at all. This is not the only Jewish belief about the afterlife. The Tanakh is not specific about the afterlife, so there are wide differences in views and explanations among believers.

The Hebrew Bible speaks about sheol (שאול), the underworld to which the souls of the dead depart. The doctrine of resurrection is mentioned explicitly only in Daniel 12:1-4 although it may be implied in several other texts. Later Judaism accepted that there would be a resurrection of all men (cf. Acts 24:14-15) and the intertestamental literature describes in more detail what the dead experience in sheol. By the second century BC, Jews who accepted the Oral Torah had come to believe that those in sheol awaited the resurrection either in comfort (in the bosom of Abraham) or in torment. 

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Adam and Eve condemned to mortality. Hans Holbein the Younger, Danse Macabre, 16th centuryChristian theology holds that Adam and Eve lost physical immortality for themselves and all their descendants in the Fall of Man, though this initial "imperishability of the bodily frame of man" was "a preternatural condition."

According to the book of Enoch, the righteous and wicked await the resurrection in separate divisions of sheol, a teaching which may have influenced Jesus' parable of Lazarus and Dives. Christians believe that every person that believes in Christ will be resurrected; Bible passages are interpreted as teaching that the resurrected body will, like the present body, be both physical (but a renewed and non-decaying physical body) and spiritual.

Contrary to common belief, there is no biblical support of 'soul immortality' as such in the New Testament. The theme in the Bible is 'resurrection life' which imparts immortality, not about 'soul' remaining after death. Luther and others rejected Calvin's idea of soul immortality. Specific imagery of resurrection into immortal form is found in the Pauline letters:

Behold, I shew you a mystery; We shall not all sleep, but we shall all be changed,
In a moment, in the twinkling of an eye, at the last trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed.
For this corruptible must put on incorruption, and this mortal must put on immortality.
So when this corruptible shall have put on incorruption, and this mortal shall have put on immortality, then shall be brought to pass the saying that is written, Death is swallowed up in victory.
O death, where is thy sting? O grave, where is thy victory?
The sting of death is sin; and the strength of sin is the law.
But thanks be to God, which giveth us the victory through our Lord Jesus Christ.
Therefore, my beloved brethren, be ye stedfast, unmoveable, always abounding in the work of the Lord, forasmuch as ye know that your labour is not in vain in the Lord. —1Corinthians 15:51-58

In Romans 2:6-7 Paul declares that God "will render to every man according to his deeds: To them who by patient continuance in well doing seek for glory and honour and immortality, eternal life", but then in Romans 3 warns that no one will ever meet this standard.

After the Last Judgment, those who have been born again will live forever in the presence of God, and those who were never born again will be abandoned to never-ending consciousness of guilt, separation from God, and punishment for sin. Eternal death is depicted in the Bible as a realm of constant physical and spiritual anguish in a lake of fire, and a realm of darkness away from God. Some see the fires of Hell as a theological metaphor, representing the inescapable presence of God endured in absence of love for God; others suggest that Hell represents complete destruction of both the physical body and of spiritual existence.

N. T. Wright, a theologian and, as Bishop of Durham, the Anglican church's 4th most senior cleric, has said many people forget the physical aspect of what Jesus promised. He told Time: " Jesus' resurrection marks the beginning of a restoration that he will complete upon his return. Part of this will be the resurrection of all the dead, who will "awake", be embodied and participate in the renewal. John Polkinghorne, a physicist and a priest, has put it this way: "God will download our software onto his hardware until the time he gives us new hardware to run the software again for ourselves." That gets to two things nicely: that the period after death is a period when we are in God's presence but not active in our own bodies, and also that the more important transformation will be when we are again embodied and administering Christ's kingdom." [36] This kingdom will consist of Heaven and Earth "joined together in a new creation", he said. 

Roman Catholicism
Catholic Christians teach that there is a supernatural realm called Purgatory where souls who have died in a state of grace but have yet to expiate venial sins or temporal punishments due to past sins are cleansed before they are admitted into Heaven. The Catholic Church also professes a belief in the resurrection of the body. It is believed that, after the Final Judgement, the souls of all who have ever lived will be reunited with their resurrected body. In the case of the righteous, this will result in a glorified body which can reside in Heaven. The damned, too, shall reunite body and soul, but shall remain eternally in Hell. 

Jehovah's Witnesses
Jehovah's Witnesses believe the word soul (nephesh or psykhe) as used in the Bible is a person, an animal, or the life a person or animal enjoys. Hence, the soul is not part of man, but is the whole man — man as a living being. Hence, when a person or animal dies, the soul dies, and death is a state of non-existence, based on Ezekiel 18:4. Hell (Hades or Sheol) is not a place of fiery torment, but rather the common grave of humankind, a place of unconsciousness.

After the final judgment, it is expected that the righteous will receive eternal life and live forever in an Earth turned into a paradise. Another group referenced as "the little flock" of 144,000 people will receive immortality and go to heaven to rule as Kings and Priests. Jehovah's Witnesses make the distinction that those with 'eternal life' can die though they do not succumb to disease or old age, whereas immortal ones cannot die by any cause.[40] They teach that Jesus was the first to be rewarded with heavenly immortality, but that Revelation 7:4 and Revelation 14:1, 3 refer to a literal number (144,000) of additional people who will become "self-sustaining", that is, not needing anything outside themselves (food, sunlight, etc.) to maintain their own life. 


A non-doctrinal illustration of the Mormon Plan of salvation.In Mormon theology, there are three degrees of glory which are the ultimate, eternal dwelling place for nearly all who lived on earth. Prior to mortal birth individuals existed as men and women in a spirit state. That period of life is also referred to as the first estate or Pre-existence. Mormon theologians cite a Biblical scripture, Jeremiah 1:5, as an allusion to the concept that mankind had a preparation period prior to mortal birth: "Before I formed thee in the belly I knew thee; and before thou camest forth out of the womb I sanctified thee, and I ordained thee a prophet unto the nations". Joseph Smith, Jr., the founder of the Latter Day Saint movement, provided a description of the afterlife based upon a vision he reportedly received, recorded within the Mormon canonical writings entitled Doctrine and Covenants.[43] According to this section of LDS scripture, the afterlife consists of three degrees or kingdoms of glory, called the Celestial Kingdom, the Terrestrial Kingdom, and the Telestial Kingdom. The few who do not inherit any degree of glory (though they are resurrected) reside in a state called outer darkness, which, though not a degree of glory, is often discussed in this context. The only ones who go there are known as "Sons of Perdition". 

Other Christian beliefs
The doctrine of conditional immortality states the human soul is naturally mortal, and that immortality is granted by God as a gift. The doctrine is a "significant minority evangelical view" that has "grown within evangelicalism in recent years". 

Some sects who hold to the doctrine of baptismal regeneration also believe in a third realm called Limbo, which is the final destination of souls who have not been baptised, but who have been innocent of mortal sin. Souls in Limbo include unbaptised infants and those who lived virtuously but were never exposed to Christianity in their lifetimes. Christian Scientists believe that sin brought death, and that death will be overcome with the overcoming of sin.

The Golden Gate in Jerusalem, known as "The Gate of Eternal Life" in Arabic, as it stood in 1900 Islam
And they say [non-believers in Allah], "There is not but our worldly life; we die and live
(i.e., some people die and others live, replacing them) and nothing destroys us except time." And when Our verses are recited to them as clear evidences, their argument is only that they say,
"Bring [back] our forefathers, if you should be truthful."
Say, "Allah causes you to live, then causes you to die; then He will assemble you for the Day of Resurrection,
about which there is no doubt," but most of the people do not know.(Quran, 45:24-26)

This section needs attention from an expert on the subject. See the talk page for details. WikiProject Islam or the Islam Portal may be able to help recruit an expert. (May 2008)

Muslims believe that everyone will be resurrected after death. They undergo correction in Jahannam (Hell) if it has led an evil life, but once this correction is over, they are admitted to Jannat (Paradise) and attain immortality.[citation needed] Those that commit unforgivable evil will never leave hell. Some individuals will therefore never taste Heaven.

(Quran,002.028) "How can ye reject the faith in Allah?- seeing that ye were without life, and He gave you life; then will He cause you to die, and will again bring you to life; and again to Him will ye return."

Muslims believe that the present life is a trial in preparation for the next realm of existence. He says[man says], "Who will give life to bones while they are disintegrated?" Say, "He will give them life who produced them the first time; and He is, of all creation, Knowing." [It is Allah] He who made for you from the green tree, fire, and then from it you ignite. Is not He who created the heavens and the earth Able to create the likes of them? Yes, [it is so]; and He is the Knowing Creator. (Quran, 36:78-81)

But those who disbelieve say, "The Hour (i.e., the Day of Judgment) will not come to us." Say, "Yes, by my Lord, it will surely come to you. [Allah is] the Knower of the unseen." Not absent from Him is an atom's weight within the heavens or within the earth or [what is] smaller than that or greater, except that it is in a clear register - That He may reward those who believe and do righteous deeds. Those will have forgiveness and noble provision. But those who strive against Our verses [seeking] to cause failure (i.e., to undermine their credibility) - for them will be a painful punishment of foul nature. (Quran, 34:3-5) 

Ethics of immortality
See also Life extension—Ethics and politics of life extension
The possibility of clinical immortality raises a host of medical, philosophical, and religious issues and ethical questions. These include persistent vegetative states, the nature of personality over time, technology to mimic or copy the mind or its processes, social and economic disparities created by longevity, and survival of the heat death of the universe. 

Undesirability of immortality
The doctrine of immortality is essential to many of the world's religions. Narratives from Christianity and Islam assert that immortality is not desirable to the unfaithful:

The poor man died and was carried away by the angels to be with Abraham. The rich man also died and was buried. In Hades, where he was being tormented, he looked up and saw Abraham far away with Lazarus by his side. He called out, 'Father Abraham, have mercy on me, and send Lazarus to dip the tip of his finger in water and cool my tongue; for I am in agony in these flames.' But Abraham said, 'Child, remember that during your lifetime you received your good things, and Lazarus in like manner evil things; but now he is comforted here, and you are in agony. Besides all this, between you and us a great chasm has been fixed, so that those who might want to pass from here to you cannot do so, and no one can cross from there to us.'
—Luke 16:22-26 New International Version Translation
Those who are wretched shall be in the Fire: There will be for them therein (nothing but) the heaving of sighs and sobs: They will dwell therein for all the time that the heavens and the earth endure, except as thy Lord willeth: for thy Lord is the (sure) accomplisher of what He planneth. And those who are blessed shall be in the Garden: They will dwell therein for all the time that the heavens and the earth endure, except as thy Lord willeth: a gift without break.
—The Qur'an, 11:106-108
Physical immortality has also been imagined as a form of eternal torment, as in Mary Shelley's short story "The Mortal Immortal", the protagonist of which witnesses everyone he cares about dying around him. Jorge Luis Borges explored the idea that life gets its meaning from death in the short story "'The Immortal"; an entire society having achieved immortality, they found time becoming infinite, and so found no motivation for any action. 

Desirablity of immortality
Many religions promise their faithful an eternal paradise in an afterlife. These presume perfection, as they are part of a divine plan, and are categorically desirable.

Physical immortality is considered desirable over its counterpart, death, which to date has been inevitable for all human beings. This presumes tolerable living conditions as an incentive for perpetual life.


Trefoil knotThere are numerous symbols representing immortality. Pictured here is an Egyptian symbol of life that holds connotations of immortality when depicted in the hands of the gods and pharaohs who were seen as having control over the journey of life, the ankh (left). The Möbius strip in the shape of a trefoil knot is another symbol of immortality. Most symbolic representations of infinity or the life cycle are often used to represent immortality depending on the context they are placed in. Other examples include the Ouroboros, the Chinese fungus of longevity, the ten kanji, the phoenix, and the colors amaranth (in Western culture) and peach (in Chinese culture).