Immortality means living forever and not dying from natural causes. Some living things have "biological immortality" because their cells do not seem to have a limit on how many times they can divide, called the Hayflick limit.

Since ancient times, people have believed that gods may not die and that gods sometimes give humans the chance to live forever. In Christianity, the belief that God may give humans a physical form of immortality through the resurrection of the body at the end of time has been a central idea. Many religions and thinkers have discussed what eternal life might look like and whether a soul exists that can live forever. In religious teachings, immortality is often described as a promise from gods to humans who act with kindness or follow divine rules.

Some scientists, futurists, and philosophers have studied the possibility of humans living forever. Some suggest that human immortality might be possible in the early 2000s with new technologies, such as transferring the mind into a computer (digital immortality).

Definitions

Life extension technologies are working to find ways to help people live longer and stay healthy. Cryonics is a method that freezes the bodies of people who have died, with the hope that future medical advances might one day allow them to be brought back to life. Some animals, like hydra and planarian worms, can live without aging or dying naturally. However, these animals have body systems very different from humans, and it is not clear if similar abilities could ever be achieved in people.

In religion, immortality often refers to the belief that the body does not die or that a spiritual form of life continues after death. In ancient Egyptian, Mesopotamian, and Greek beliefs, gods were thought to have physical bodies and were considered immortal. In Mesopotamian and Greek traditions, some humans were also believed to be made physically immortal by the gods. In Christianity, many people believe that true believers will be brought back to life with physical immortality. Similar ideas about physical immortality are also found in beliefs held by Rastafarians and Rebirthers.

Physical immortality

Physical immortality is a state where a person does not die and can think clearly forever. It can mean a person lives on through something other than a body, like a computer.

Before modern science, people tried to achieve physical immortality in different ways. Alchemists, for example, tried to make the Philosopher's Stone, which was believed to grant immortality. Other cultures had stories, like the Fountain of Youth or the Peaches of Immortality, which inspired searches for a life-giving drink.

Today, scientists are exploring ways to achieve physical immortality, such as cryonics, digital immortality, and medical advances. However, these methods must solve all causes of death to work. The main causes of death are aging, disease, and injury. Scientists are researching solutions to these problems, but no single theory has yet unified all possible answers.

Aubrey de Grey, a scientist, describes aging as a collection of changes in the body’s cells and molecules that eventually harm the body and cause death. These changes include the loss of cells, DNA damage, harmful mutations, and weakened immune systems. To stop aging, scientists must find ways to fix all these issues. This process is called "engineered negligible senescence." Research also shows that aging is linked to a loss of accuracy in how molecules function.

Disease can be overcome with technology. Diseases are conditions that harm the body, which the body is not naturally designed to handle. Advances in genetics are helping scientists find cures for many diseases. Researchers are learning more about how diseases work and developing better ways to detect and treat them early. For example, stem cells may help cure diseases like Parkinson’s and Alzheimer’s. Breakthroughs in biology and research on telomeres, the ends of DNA strands, are helping treat cancer. Scientists are also working on vaccines for diseases like AIDS and tuberculosis.

Some scientists now believe aging should be classified as a disease.

Physical injuries remain a risk for someone who is physically immortal. Even if a body could repair itself from severe injuries, like with nanotechnology, the brain is still vulnerable. Protecting the brain from injury could change how people behave, making physical immortality less appealing to some.

Biological immortality means not aging. It refers to a lack of increased death risk as a person gets older. A cell or organism that does not age or stops aging is biologically immortal.

Biologists use the word "immortal" to describe cells that can divide endlessly, unlike normal cells that stop dividing due to DNA damage or shortened telomeres. The HeLa cell line, taken from a cancer patient in 1951, is the most famous example of an immortal cell. Before the 1960s, scientists wrongly believed all normal cells were immortal. Telomeres, the protective ends of DNA, shorten each time a cell divides. When telomeres are too short, cells can no longer divide and die. Telomerase, an enzyme found in stem and cancer cells, rebuilds telomeres, allowing endless division. Scientists are studying whether telomerase can help human cells avoid aging. Research on stem cells may also help grow organs for transplants, improving human life expectancy. These ideas are still being tested.

Biologically immortal organisms can still die from disease or injury, not just aging. Examples of biologically immortal species include:

• Bacteria: Bacteria reproduce by splitting into two identical cells, which can continue splitting. This process makes bacteria effectively immortal. Some studies suggest older daughter cells are weaker and more likely to die.
• Turritopsis dohrnii (a jellyfish): This jellyfish can change back into a younger form after reaching maturity, allowing it to live indefinitely. It has spread worldwide due to this ability.
• Hydra: A simple freshwater animal, Hydra has radial symmetry and can regenerate damaged parts.

The existence of biologically immortal species shows that aging is not a necessary part of life. Living things take energy from the environment and release waste, allowing them to repair themselves. Aging is thought to be a side effect of evolution, but why aging exists is still debated. Some theories suggest aging is linked to programmed cell death and the way DNA is copied.

Modern theories about why aging happens include:

• Mutation accumulation: Proposed by Peter Medawar in 1952, this theory suggests aging is not selected against by evolution because organisms reproduce before harmful mutations appear.
• Antagonistic pleiotropy: George C. Williams proposed this idea in 1957, stating that some genes help early in life but cause harm later, such as aging.
• Disposable soma theory: Thomas Kirkwood proposed in 1977 that the body must balance energy between growth, repair, and reproduction, which may lead to aging.

Religious views

As late as 1952, the editors of the Syntopicon discovered during their work on the Great Books of the Western World that "the philosophical issue concerning immortality cannot be separated from questions about the existence and nature of the human soul." Therefore, most discussions about immortality before the 21st century focused on the nature of the afterlife.

The beliefs of Christianity, Islam, and Judaism about immortality differ because each religion has its own unique teachings about the soul or spirit.

Christian theology teaches that Adam and Eve lost physical immortality for themselves and all their descendants after the Fall. This initial "unbreakable condition of the human body" was a special, non-natural state.

Christians who follow the Nicene Creed believe that all people, whether they believed in Christ or not, will be brought back to life at the Second Coming. This belief is called universal resurrection. Paul the Apostle, who once followed Jewish teachings that included the idea of a future physical resurrection, described a view of resurrection where both the physical and spiritual parts of believers are restored to match the resurrected body of Christ, who "will change our weak bodies to be like his glorious body" (ESV). This idea is similar to Paul’s statement that believers are "buried with him [Christ] through baptism into death" (ESV).

N.T. Wright, a theologian and former Bishop of Durham, has said that many people forget the physical side of what Jesus promised. He told Time magazine, "Jesus’ resurrection marks the beginning of a restoration that he will finish when he returns. Part of this will be the resurrection of all the dead, who will 'awake,' have bodies again, and take part in the renewal." Wright also said that John Polkinghorne, a physicist and priest, explained this as "God transferring our software onto his hardware until the time he gives us new hardware to run the software again for ourselves." This idea shows that the time after death (called the Intermediate state) is when people are with God but not in their own bodies, and that the most important change will come when people are again in their bodies and helping Christ rule his kingdom. This kingdom will include Heaven and Earth "joined together in a new creation," Wright said.

Christian apocrypha include stories of people like Cartaphilus, who were cursed with physical immortality for wrong actions against Christ during the Passion. The medieval Waldensians believed in the immortality of the soul. Leaders like John Asgill and John Wroe taught that physical immortality was possible.

Many early Christian writers connected the immortal rational soul to the image of God described in Genesis 1:26. Athanasius of Alexandria and Clement of Alexandria said the immortal rational soul itself is the image of God. Early Christian prayers also show this link between the immortal rational soul and the creation of humans in God’s image.

Islamic teachings include the idea of spiritual immortality. After death, Islam teaches that a person will be judged based on their beliefs and actions and will go to an eternal place. A Muslim who follows the five pillars of Islam will enter Jannah, where they will live forever. In contrast, a kafir (someone who does not believe in Islam) will go to hell.

Angels in Islam are considered immortal from the Islamic perspective, though some people believe angels will die, and the Angel of Death will also die. However, there is no clear text about this. Jinn, spiritual beings, have very long lifespans, sometimes between 1,000 and 1,500 years. Khidr, a figure in Sufism, is given immortality as an exception. In Islam, Jesus was taken to heaven by Allah to protect him from the cross and to give him long life until the arrival of the Dajjal. The Dajjal is also given a long life. Jesus will send the Dajjal away after 40 days, with each day lasting a year, a month, a week, and the rest of his days as normal. The Qur’an says that all life, including humans, will eventually end in death.

The idea of an immaterial and immortal soul separate from the body was not present in Judaism before the Babylonian exile but developed later through interactions with Persian and Greek ideas. The Hebrew word nephesh, often translated as "soul" in older Bibles, actually means "living being." In the Septuagint (a Greek translation of the Hebrew Bible), nephesh was translated as psūchê, the Greek word for "soul."

The Hebrew word nephesh, which is translated as "soul" in English Bibles, refers to a living, breathing body, not an immortal soul. In the New Testament, the Greek word psūchê, also translated as "soul," has the same meaning as nephesh, without mentioning an immortal soul. The word "soul" can refer to the whole person or self, as in the example of "three thousand souls" converted in Acts 2:41 (see Acts 3:23).

The Hebrew Bible mentions Sheol, originally a synonym for the grave or the place where the dead rest. Sheol was seen as the end of existence until the resurrection of the dead. This idea of resurrection is clearly stated in Daniel 12:1–4, though it may be implied in other texts. New ideas about Sheol developed during the intertestamental period (the time between the Old and New Testaments).

Jewish views on immortality are best understood through references from the Second Temple period. The idea of the physical body being resurrected is found in 2 Maccabees, which describes the recreation of flesh. Detailed descriptions of resurrection appear in non-canonical texts like the Book of Enoch and the Apocalypse of Baruch. According to scholar P.R. Davies, the Dead Sea Scrolls contain little or no clear mention of imm

Philosophical arguments for the immortality of the soul

Alcmaeon of Croton believed that the soul is always moving and never stops. The details of his argument are not clear, but it may have influenced later thinkers like Plato, Aristotle, and others.

In Plato’s Phaedo, four arguments support the soul’s immortality:

• The Cyclical Argument (Opposites Argument): Plato claimed that Forms, such as beauty or justice, are eternal and never change. Since the soul gives life, it must also be eternal and cannot die. The body, however, is physical and can die. Plato compared this to fire and cold. If cold is unchanging, then fire, its opposite, must remain whole when it moves away, just as the soul remains whole when the body dies. This is similar to how opposite magnetic poles repel each other.
• The Theory of Recollection: Plato argued that people are born with knowledge they did not learn from experience, such as understanding the concept of equality. This suggests the soul existed before birth and carried this knowledge. A similar idea appears in Plato’s Meno, where Socrates implies that all knowledge is remembered from a previous life, though he is less certain in Phaedo.
• The Affinity Argument: Plato stated that invisible, immortal, and non-physical things differ from visible, physical, and dying things. The soul belongs to the first group, while the body belongs to the second. When the body dies, the soul continues to live.
• The Argument from the Form of Life: Plato argued that Forms, such as beauty or life, are unchanging and cause everything in the world. All things share in these Forms. For example, beautiful things share in the Form of Beauty. The soul shares in the Form of Life, meaning it cannot die.

Plotinus proposed an argument called “The Achilles of Rationalist Psychology,” which Kant later named. Plotinus claimed the soul is simple, meaning it cannot be broken into parts. If something is simple, it cannot decompose. Many later thinkers, including Moses Mendelssohn, also argued that the soul is simple and therefore immortal. Mendelssohn’s Phaedon expands on this idea, addressing weaknesses in earlier arguments.

Theodore Metochites argued that the soul moves itself. However, movement stops only if the cause of movement separates from what is moved. Since the soul and body are one, movement cannot stop, suggesting the soul continues after death.

Avicenna believed the soul and body are separate, and the soul cannot be destroyed.

Thomas Aquinas explained the soul’s immortality in Question 75 of the Summa Theologica, building on Aristotle’s ideas.

René Descartes agreed that the soul is simple and cannot break apart. However, he did not consider the possibility that the soul might suddenly vanish.

Gottfried Wilhelm Leibniz supported the idea that the soul’s simplicity leads to its immortality, but like others, he did not address the possibility of the soul disappearing. In his Monadology, he introduced a new argument for the immortality of monads.

Mendelssohn’s Phaedon is a book with three dialogues that revisits Plato’s Phaedo, where Socrates discusses the soul’s immortality before his death. Mendelssohn improved earlier arguments about the soul’s simplicity and immortality. He also added new ideas, such as the soul’s ability to keep its reasoning abilities as long as it exists.

Ethics

The possibility of living forever without getting sick or dying brings up many medical, philosophical, religious, and ethical questions. These include situations where people are alive but cannot think or move, how a person’s personality might change over time, technology that could copy or mimic the mind, the unfair advantages that might come from living much longer than others, and whether life could continue after the universe ends.

Some stories imagine living forever as a kind of suffering. For example, in the myth of Tithonus, a man is made immortal but loses the ability to age, leading to endless pain. In Mary Shelley’s story The Mortal Immortal, the main character lives for many years while everyone he loves dies. For more examples from books and movies, see Immortality in fiction.

In 2012, Kagan argued that living forever would not be a good thing. He presented a dilemma: either a person’s character stays the same over time, or it changes completely.

• If a person’s character stays the same—meaning they keep the same desires, interests, and goals—they might eventually become bored and find endless life too dull to enjoy.
• If a person’s character changes greatly, such as by losing memories or gaining a completely different kind of mind, they would no longer be the same person, and it would not matter much what happened to them.

Kagan believed that either situation would make immortality unpleasant. He suggested that the best outcome would be for people to live as long as they want and then accept death as a way to avoid the endless boredom of living forever.

Sociology

If humans could live forever, the world's social systems might change. Sociologists say that knowing we will die affects how people act. As medical technology improves and helps people live longer, society may need to think carefully about how social structures could change. The world is already seeing changes in population patterns, with more older people and fewer children being born. The ways society adapts to these changes might help predict how a world with immortal people could look.

Sociology has studied the idea of immortality, including how people try to live forever (either literally or symbolically) in the 21st century. These efforts include paying more attention to the dead in Western cultures, creating online memorials, and using science to help people live longer. These attempts to achieve immortality and their effects on society have led some experts to suggest that we may be moving toward a "Postmortal Society." Changes in society caused by the pursuit of immortality could affect how people think about the world, institutions, and the balance between technology and nature.

If humans lived forever, the population would grow, which could lead to challenges, such as how more people would affect the environment and the Earth's natural limits.

Politics

Some scientists believe it is possible to greatly extend human life by slowing or stopping the aging process. However, there are no official government programs worldwide that focus on stopping aging or significantly extending life. In 2012, political groups supporting the idea of immortality were created in Russia, the United States, Israel, and the Netherlands. These groups aimed to support research into anti-aging technologies and promote the goal of achieving life without aging, eventually leading to immortality. Their goal was to ensure these technologies could be available to many people who are currently alive.

Some experts criticize the growing interest in immortality projects. One scholar, Panagiotis Pentaris, suggests that ending aging as a cause of death might increase differences between social classes and create greater inequality. Others argue that efforts to achieve immortality, such as digital immortality, life extension, and cryonics, are linked to systems that benefit wealthy individuals. In this way, the pursuit of immortality may become a major issue in the 21st century, involving conflicts between those with wealth and those without.

In 2025, during the China Victory Day Parade, General Secretary of the Chinese Communist Party Xi Jinping and President of Russia Vladimir Putin discussed topics related to organ transplants and "immortality." This conversation was recorded and broadcast by China Central Television. Putin mentioned biotechnology and stated that "human organs will continue to be transplanted, and people will become younger and younger." Xi responded by noting that some experts predict life expectancy could reach 150 years and that 70 years old is still relatively young compared to the past. Later that evening, at a press conference, Putin confirmed to Russian media that he and Xi had discussed the topic of human lifespan.

Symbols

There are many symbols that represent immortality. The ankh is an Egyptian symbol of life that shows immortality when shown in the hands of gods and pharaohs, who were believed to control the journey of life. The Möbius strip shaped like a trefoil knot is another symbol of immortality. Many symbols that show infinity or the life cycle are used to represent immortality, depending on where they are used. Other examples include the Ouroboros, the Chinese fungus of longevity, the ten kanji, the phoenix, the peacock in Christianity, and the colors amaranth (in Western culture) and peach (in Chinese culture).