Chapter 8 – When Does A Life Begin?

Does a life start at conception, birth, some time in between, or at a different time altogether? Does this also apply to non-human lives? What is a life? What is life? What does “alive” mean?

Is life sacred? What kinds of life are sacred? What makes them sacred? What does “sacred” mean?

Heated ethical arguments about such issues can arise when some kinds of research or practices or legislation are contemplated. The answer given to the question depends on the answerer’s beliefs about the fundamental nature of life.

In Chapter 3 Monism and Dualism: A case for the existence of the supernatural and in Chapter 4 The Nature of the Supernatural, where I discussed three things that might possibly point to the existence of a supernatural entity, one of the three was the difference between a living organism and inert matter. This chapter, which considers the contentious issue of when a life, and in particular a human life, begins, discusses arguments from both materialist and supernatural perspectives. It will look at some aspects of the concept of life, the history of life on Earth, and some characteristics of organisms from the very simple to the very complex.


What is Life?

Life is the property or quality that distinguishes living organisms from dead organisms and other inanimate matter. But this simple description omits to say how to make the distinction. Some life forms seem inanimate at first sight, for example spores or slime. And continued argument about how to decide exactly when human death occurs, with such concepts as brain death replacing earlier concepts such as cessation of heartbeat or breathing, shows that the criteria for being alive are uncertain.

A common biological definition is that living organisms possess four properties:

  • metabolism – using material and energy from the environment to support continued functioning;
  • growth – increasing in size from infant to adult;
  • reproduction – producing, from within the bodies of living parents, new separate organisms that become similar to their parents;
  • response or adaptation to the environment – taking action needed for metabolism, growth, reproduction and safety.


Other definitions specifically require also that living beings move, communicate, evolve, keep their internal environment stable, have feelings, are intelligent, are conscious, or function using chemical reactions (as distinct from being the product of manufactured electronics).


I think that some of these conditions that have been suggested to be necessary for life are inappropriate or too stringent. Some organisms, lichens for example (which actually are symbiotic composites of more than one kind of organism), drift to rocks and other surfaces and then attach themselves permanently. They grow but never move. Some organisms that are able to live in very diverse environments do not keep their internal environment stable, but adjust it to suit their external conditions. Many species of plants appear not to move, although they can be pushed out of shape by external forces and unless broken return to their previous shape.. We have no way of knowing whether organisms that are markedly different from us are conscious and have feelings. Their reactions to their environment might be conscious or just unconscious intelligence. Much of our own interactions are unconscious. And every organism needs some kind of intelligence to perform the four necessary functions as described earlier in the biological definition of living organisms. (As I have explained in the essay Data, Information, Meaning, Intelligence and Consciousness, in the Sundry Musings part of my website, I think intelligence is, among other things, a representation of the operations of the laws of physics).


A definition that invoked the science of thermodynamics first appeared in the book What is Life written by the famous quantum theorist Erwin Schrödinger. He said that living beings are “the class of phenomena that are open or continuous systems able to decrease their internal entropy at the expense of substances or free energy taken in from the environment and subsequently rejected in a degraded form.” (Entropy is briefly described in Chapter 12 Randomness.) This very mechanistic and abstruse definition does not address growth or reproduction. However, the concept is used in the search for signs of life in other parts of the universe, where the by-products of life are the only signs detectable from Earth. Scientists look at distant planets to see if there is evidence of chemicals that would normally react together. If at least one such chemical would normally have disappeared but is found to be still there, then it is assumed that its presence is the result of some living organism continuing to produce it.

An even broader definition of life is favoured by the cosmologist and astrobiologist Charley Lineweaver. (Astrobiology is the scientific investigation of possible life forms that might exist in places other than Earth.) Lineweaver suggests that life is “a far-from-equilibrium dissipative system”. It is sufficient to say here, without attempting to go into the physics of what this means, that dissipative systems include such things as hurricanes as well as living organisms.

My reason for including these two definitions is to illustrate that our usual concept of living organisms is determined very precisely by the conditions under which life can exist on Earth, and to suggest that widely differing forms of life might exist elsewhere. Having a wider view of what constitutes life may give a different perspective about moral or philosophical issues relating to it. (I do not, of course, consider the hurricanes that we are familiar with to be living organisms.)

The other different definitions reflect different views about the essential nature of life on Earth. Some people think certain types of things are alive that other people think are not. Bacteria, fungi and plants are always included as life forms. Things, such as fire, machines, virtual life and viruses, all of which can have some lifelike characteristics, are commonly excluded.

Viruses have no metabolism: they neither take in nourishment nor grow. They do not reproduce, but may be replicated whenever their DNA or RNA gets into cells of living organisms. However, they are given identification by the use of taxonomic names in the same way as living organisms. They can be mutated and evolved into new strains, and hence they appear to act as if they are alive. Because of these characteristics, viruses are treated in a similar way to living organisms in the practice of medicine (taking due regard of the different characteristics of organisms and viruses). The term “live virus” is used to distinguish an intact virus from one that has been made ineffective, for example for use in a vaccine. Viruses do not have a lifespan: they will continue indefinitely until some external agency damages them.

Whatever the precise details of the definition may be, if life is to perform at least some of the four basic functions, then it must depend on a functioning system, that is, a sustainable arrangement of interworking parts. This means that, for a typical specimen of a form of life, its parts and their interaction must be able to operate in the conditions of its environment, such as the temperature, the pressure, the winds and the presence or absence of particular chemicals.


(It is interesting to compare what the astrobiologists are looking for with what the SETI project (Search for Extraterrestrial Intelligence) is looking for. The astrobiologists are using interferometers to identify chemicals on identified planets of distant stars. The signs of life forms that they detect may have been produced by organisms that are no more complex than our bacteria. The SETI team is using radio telescopes to detect signals that might have been emitted by possible distant communities that have developed sophisticated technologies “similar to ours”. What kind of life form, if any, would some far distant advanced community think inhabited Earth?)


All the discussion above refers to purely physical processes. Could something else, something supernatural, be needed to let inert matter become alive? People who believe that a supernatural element is necessary for life usually feel that this makes life special, or sacred, so that it must be preserved wherever possible. However, the same people often regard the lives of most non-humans organisms to have little or no significance.

If there were a sequence of small steps from inanimate material to living organism, would there be a step that would allow or need a supernatural element? At present no plausible set of steps has yet been proposed. Most biologists who have looked into this matter think any process from inanimate matter to life would require a very unlikely series of coincidences. What role would the supernatural play in bringing these coincidences together? These questions relate to my case for the possible existence of some supernatural entity. (See in Chapter 3 Monism and Dualism: a case for the existence of the supernatural.) Can such a sequence of steps be demonstrated? How did life initially come into being?



Origins of Life on Earth

How did life originate on Earth? Three suggested processes are evolution, intentional creation and reincarnation. (I use the term intentional creation rather than intelligent design for two reasons. A design is not a production process nor the thing designed but only a plan. And also, I want to emphasise the contrast between a deliberate act of intention and the processes of nature where every outcome is just the necessary result of the available materials and conditions of the particular environment.)

From a different perspective, I would suggest three ways by which life came or could come into being:

  • life is an emergent property of matter, with an evolutionary process being responsible for producing the structure from which life “emerged” out of inanimate material. (For an explanation of emergence see Chapter 10 Reductionism and Emergence.);
  • all matter including fundamental particles is intrinsically alive, that is, life is purely material and is not just an emergent consequence of the way matter is arranged as an organism;
  • a supernatural element is necessary to impart the four biological properties to a properly structured piece of inanimate matter to give it life, and (in some versions) to give shape and function to the various kinds of organism, all of which is compatible with both intentional creation and reincarnation but does not address how the complex bodies of organisms came into being.


Most biologists assume that life developed from inanimate matter through a natural process of evolutionary steps. Increasingly complex structures developed in each step. These included types of chemicals that can cause the assembly of copies of themselves when they are mixed with the right ingredients. In this concept, the origin of life was not a single event of “switching on”: it emerged as a gradual increasingly complex material process. (Some scientists, notably Chandra Wickramasinghe and Fred Hoyle, have proposed that life on Earth began from life forms or pre-life forms that arrived from outer space. But this does not answer the basic question.)

Some types of self-replicating chemicals occur in nature and others have been manufactured. Scientists have been using them in trying to produce new living organisms. (This is not the same as putting DNA – either modified from another organism or artificially generated – into a living organism.) But if they were to succeed, this would not be a re-enactment of how life originally emerged from inanimate matter but a process of intentional creation – but not by the creator envisaged by creationists. It might, however, demonstrate the feasibility of the evolutionary concept. There is no accepted scientific theory of how living organisms came to exist: Darwin’s theory of evolution addresses only how there came to be many different life forms.

Biologists and other scientists have identified a lot of things that they think would need to happen for life to be able to emerge from inanimate matter. They have shown how some of the required chemicals, including strings of RNA, could have occurred naturally. They have shown how membranes could be formed to wrap around the RNA and other items to create an organism. But for the RNA to be able to recreate itself, in addition to the other materials, and assemble them so they form a living organism would require a very unlikely series of coincidences.

But even this would not have been enough.

In addition to the things specified in the description of life, every living organism must be able to recognise the aspects of its environment that are relevant to its needs of metabolism, growth, reproduction and safety. It must also have the ability to perform the appropriate actions for each of these. And it also must have the compulsion to respond to its needs at the appropriate time and to the appropriate degree. For example, it must know what to eat, what not to eat, when to eat and how much. It must be compelled to look for food if no food is readily available.



It is often assumed that any extraterrestrial life, such as life on other planets, would have similar origins to life on Earth. Organisms developing in very different environments might need to be structured around different chemicals, such as ammonia instead of water or silicon instead of carbon, or merely using structures different from DNA. This would make them different from life as we know it, but, to be life, they would probably need to be compatible with the biological (and the thermodynamic) definition.


Some people claim that a life force is a necessary part of all organisms, so that while natural processes can produce the body, something else is needed to “switch it on”, i.e., to give it life. The late Australian biologist Charles Birch suggested that this force is an aspect of the material world. Others say it is supernatural. James Le Fanu, who was mentioned in Chapter 3, refers in his books to a life force that is separate from the laws of reductionist science and is involved in both life and consciousness, but it is not clear whether he regards it as an aspect of the material world or of the supernatural. (The philosopher David Chalmers, in his book The Conscious Mind, argues that no explanation of consciousness based on physical terms, i.e., on principles that comply with the laws of science, is logically possible. He says any explanation must be based on “psychophysical laws”, which would still be material not supernatural. To me, that seems to be either a contradiction in terms or an implication that there is some still-to-be-discovered branch of physics as was speculated in the last few paragraphs of Chapter 4.)


Proponents of intentional creation assume a transcendent creator for all life on Earth, and attribute some supernatural aspect to all or some living organisms. This may mean either that the creator produced only the very first organism, or the first of each of the different forms which then reproduced naturally, or that each new individual is separately created. There is often the implication that what is alive in each particular organism is the supernatural spirit not the material body, with the individual (supernatural) identity usually continuing after the death of the biological body.

Reincarnation means that every life is a supernatural entity that inhabits a succession of material bodies (not necessarily all human) each of which is born and dies. The beginning of the biological body may be of no great concern. The supernatural entity may exist in waiting between the death of one host and the birth of the next. Again, in this concept it is the supernatural that gives life to the body. So most lives began a long time ago when something new appeared that did not have another piece of supernatural waiting for it.

These pieces of the supernatural do not meet the biological criteria of growing, reproducing and having a metabolism. They are thought of as the conscious driving force of each body, and perhaps the intelligence, sometimes with claimed memory of previous incarnations.

In some traditions, reincarnation implies that each serial life remains as a separate identity until such time as it reaches a condition of perfection when it can merge into some universal supernatural. There is no explanation of how new sequences of reincarnation come into being as the number of living bodies on Earth increases, nor, if the population decreases, how a sequence would cease without achieving perfection.


Development of Life on Earth

Views about how life originated on Earth have their counterparts in the various views about how it subsequently developed. The evolutionary view, that natural processes produced the diversification and development of life on Earth, is derived from the findings of biological and geological science. The other views either accept some role for natural evolution, including evolution being occasionally nudged onto a new path by the supernatural, or claim that, while variation occurs within species, all species are the consequence of specific creation.

Geological evidence points to bacteria and other forms of life existing at least 2.7 billion and possibly 3.8 billion years ago. The first living entities on Earth would probably have consisted of something like individual microscopic films enclosing RNA or DNA, which controlled the organisms’ functioning and reproduction. According to the theory of evolution, they diversified into multitudinous forms of bacteria that proliferated and occupied many parts of the earth’s surface. Evidence also points to the appearance, after more than billion years, of eukaryotes, i.e., organisms with their genetic material enclosed in a nucleus. (The earlier organisms, bacteria and archaea, are known as prokaryotes) There are no multicellular prokaryotes, but there are signs of multicellular eukaryotes at about 700 million years ago. These developed into increasingly complex organisms – animals, plants, fungi and protozoans.

In simpler types of single-cell organisms, reproduction consists in the cell growing and then splitting into two or more cells that are like smaller versions of the cell that split. This is referred to as cell division. Cells resulting from the division are occasionally slightly different from the parent cell, which can lead to the development of new species.

Cell division also occurs within most of the cells of multicellular organisms, in fact this is the main process in the growth of these organisms. During these organisms’ lives, cells are continually dying and being replaced by the division of other similar cells.

In the most common type of reproduction by division, each “daughter” cell is a half of the parent. (Some kinds of bacteria produce one or more daughter cells that are much smaller, fully functional, versions of the parent.) Each succeeding generation is, in a sense, just a continuation of its predecessor. All individual organisms have arisen from being parts of previously existing organisms.


Unity of Life

The processes of reproduction, mutation, separation and combination of all known life forms on Earth are controlled by DNA (and RNA). Many types of microorganism readily exchange segments of their DNA, often incidentally giving recipients new abilities or features. In genetic engineering, segments of DNA are deliberately transferred from one species to another – often very remotely related – species to provide the recipient with some specific additional characteristic. There is evidence that cross-fertilisation continually occurs between eukaryotes (including us) and bacteria (and viruses), with the progeny acquiring characteristics of both “parent” species, and passing them on to further generations. An interesting example is a species of snail that is green. It has acquired plant genes to produce chlorophyll. The snails turn red in autumn.

Almost all eukaryotes have other types of organisms living within their bodies, some providing essential processes for the hosts, and some parasitic. There are about ten times as many “non-human” organisms in a human body as cells of the body itself. (But the host cells are very much larger than the resident organisms, and comprise most of the total body mass.) It is Evidence suggests that eukaryotes arose as a result of single-cell bacteria becoming functionally incorporated into the bodies of single-cell archaea, with the nucleus and mitochondria of each subsequent eukaryotic cell being descendents of incorporated bacteria.

In contrast to reproduction by cell division, sexual reproduction is a process that employs the fusing of very different specific types of parts of two biologically compatible but distinguishable organisms, usually of the same species. However, the concept of species, in fact the whole concept of classifying life into domains, kingdoms and so on down to genera and species, while very useful, does not mean that life is rigidly divided into these categories. There are many cases where the distinction between species is not clearly definable.

Most biologists think that all existing life on Earth has probably descended from the same common ancestor. There are some process used by all life forms from the simplest bacteria and archaea to the most complex eukaryotes, and they are all controlled by virtually the same kind of DNA and RNA. So it seems that all life on Earth has been one biological unity since then. From this point of view, there are new arrangements of living matter but no new beginnings of life.


(It could be argued that, since bacteria and archaea have different outer coatings, they might have arisen separately without a common ancestor. However, both operate and are structured in accordance with patterns of DNA and RNA, and the differences in membrane composition are not very great: the membranes of bacteria consist mostly of glycerol-ester lipids, and those of archaea mostly glycerol-ether lipids. So separate origins would seem very unlikely.)



Individual Identity

Notwithstanding biological unity, there is a distinction between life and a life. Organisms can be seen to be spatially separate from each other, distinctly recognisable from each other, independently capable, and differently intelligent and emotional. They are individual lives that come into being and die.

Parts taken from the bodies of some plants and animals can be grown to become mature organisms or body parts. New plants can be grown from cuttings or from the culture of individual cells. Small parts from some animals, for example planarian worms and some jellyfish, can regenerate into complete organisms provided that they contain some of each type of the animal’s tissues. Organs can be transplanted between compatible complex animals of the same species. These are examples of both unity and difference suggest that the individual parts, including cells, of multicellular species are separately alive.


But what exactly is an individual life and when does it begin? Is a full-grown cell the same entity that it was when it just started to grow? Is it still the same entity after it has split into two? Most people would probably agree that a single cell organism is one entity before it splits, but two new separate entities afterwards, able to go their separate ways. So for single cell organisms that reproduce by division, life as an organism begins (and ends) at the moment of splitting. But what about the multicellular organisms that usually do not reproduce by splitting into similar parts?

Most complex multicellular organisms reproduce through the sexual process – the uniting of two dissimilar cells, a sperm and an egg. This seems to be a reverse process to cell division, but the new cell is significantly different from either of the cells it was formed from.

The process by which eukaryotes reproduce from fertilised female cells differs across the range of species. Plants form from seeds that have to depend on being in a suitable location and supplied with water. Many species, such as plants and some fish, produce sperm and eggs that are fertilised when external agents bring them together outside the bodies of the parents. Many other species produce eggs that are fertilised inside the mother and hatch outside the body of the mother. The time of the beginning of the life of individual members of these species would probably be arbitrarily assigned to the time that they start to emerge from their birth shell. The remaining discussion will consider the beginning of the lives of only those species that develop to birth within the body of the mother, with emphasis on mammals.


Multicellular organisms can be thought of as associations of cells whose interactions make the unit a new living entity. But there are degrees of coherence in associations. Slime moulds are types of single-cell organisms that normally hunt as a herd, feeding on other microorganisms. Under stressful conditions the individual slime microbes form coherent associations looking and acting like slugs or fungi, with differentiated body parts. Then some individual members may become spores that will awaken and produce new colonies when conditions improve, while many of the other members die. These and other types of associations – such as corals, for example, which are polyps symbiotic with algae – are loosely held together, and the members are still separate organisms.

Some loose associations may cease to exist without any of the members dying, as when a stressed slime mould structure disassembles upon conditions becoming favourable. In more complex associations, the members form differentiated groups, i.e., organs, that depend on each other for survival. Failure of an organ such as the heart or liver can cause the whole association, i.e., the body, to die. The more strongly they depend on each other, the greater the likelihood that all cells will die if the association ceases to exist. Very complex (multicellular) organisms, including humans, are strongly interdependent associations, and usually all cells die from lack of support when the organism dies. But as mentioned earlier, it is possible for individual cells to be artificially kept alive, to divide and grow. Also, the association itself can survive if it loses larger parts that are useful but not essential, in animals for example, a leg or an eye.


Sperm and eggs do not have the functionality that allows them to exist as organisms, and the composite fertilised egg cell initially lacks these functions. New bodies develop by single-cell eggs continually dividing into more and more cells which remain coherently associated but become differentiated into specialised organs. Their functioning as organised units develops incrementally. At some stage the association becomes the life of the new multicellular organism, superseding the separate lives of its members.

So, while the life of a new (single cell) prokaryote may be said to begin with the division of its parent cell, different criteria are needed to identify the beginnings of mammalian lives.

The philosopher Peter Singer has suggested it would be humane to euthanise babies whose disabilities would make their lives so miserable as to greatly outweigh any pleasure that they might experience. In his view their life as persons should be considered to begin when they were 30 days old. After that age, euthanising them would be regarded as murder. This choice of 30 days seems to be arbitrary. Some people would put the beginning at some time before birth. How could any such date be justified?


What Identifies the Beginning of an Individual Mammalian Life?

Biological Criteria

From a biological point of view, some possible criteria for identifying the beginning of a multicellular mammalian life are:

  • separation;
  • independence;
  • activity;
  • stage of development;
  • degree of being alive.

It would be consistent for these criteria to be applied equally to all species of organism.



In this context, separation means that the new life is physically separated from or not a part of any other organism. The obvious example is a baby at or soon after birth. This may suggest that a baby that is removed from the womb by caesarean section before its full term begins its life earlier than it would have if it had been allowed to proceed to natural birth. There would be argument about how separate an unborn foetus or baby is. And conjoint twins are not separate but are separately alive and have individual lives.

But being separate does not necessarily mean that something is, or is yet, a new life. A kidney removed for transplanting is not a life, even though it is living. This suggests that a new life might begin when a foetus begins to have an active mind. But at what stage of the development of a nervous system and a brain does that begin?



No form of life is completely independent: all are dependent on their environment for food and energy, and often for cooperative assistance. But there is a difference between passive dependence where all the action to sustain life is taken by the environment, as with a new foetus which is completely supported by its mother, and “active dependence” where the organism takes action to provide for its own food and safety. We usually regard such active dependence as independence. But there are different stages of how much action a developing body takes, and how much the environment, including other organisms, actively gives. So if independence is to be a criterion for the beginning of a life, the decision of when it is sufficiently independent must be arbitrary. It might, for example, be claimed that the beginning of its life is when it has independently developed certain capabilities, such as an animal when it has been weaned and can forage. So this could be some time after birth.

(After we are born we are never independent of the billions of microorganisms that reside within our bodies, but I do not think this is relevant to this particular criterion.)



Activity comprises self-generated motion of all or part of the organism or its interior processing. Seeds and spores are quite inactive and presumably have not yet begun their lives before they begin to germinate. But apparent inactivity does not necessarily mean absence of life. A few years ago a bacterium that had been locked beneath a Greenland ice sheet for more than 120,000 years was revived by scientists at Pennsylvania State University by slowly warming it in an incubator over a period of 11 months. After being placed in a nutritious environment it began producing fresh colonies. When discovered it had been under three kilometres of ice. So life can be in a condition of inactivity for a long time. This particular case has little to do with the beginning of life, but it might suggest that if life begins at the moment of fertilisation, it could be inactive but still alive for a long time. But, as discussed earlier, there is a difference between life and a life.

At some stage of development a foetus starts to move in the womb, initially without its movements being detectable by its mother. Perhaps its life could be considered to begin when it first moves parts of its body or limbs. It would be difficult to determine when this occurred for each individual foetus, and the earlier movements would be involuntary. Although some arbitrary date could be chosen, based on average times after conception, this does not seem to be a useful criterion for issues of moraity.


Stage of Development

Stage of development could refer to the creation of processes such as heartbeat or the appearance of a brain. Or it could refer to the progressive acquisition of new faculties and capabilities such as mobility, intelligence and consciousness.

But what is the significance of a pulsating heart? A heart, which is essentially a pump, can continue beating when it is removed from the body, and an artificial heart can produce a constant flow of blood instead of a pulsating one. But a heart does not itself signify an individual life. Also, the existence of a rudimentary brain does not in itself confirm the beginning of a new life. But some stage in the development of its functions might.

To survive, all organisms must be able to distinguish between what is food and what is not, and whether an environment is safe and favourable or not. Survival also requires knowing how to respond in each type of event that it encounters. Organisms we would regard as extremely simple or primitive have a range of faculties in a form sufficient for their needs. For example, the gut bacterium Escherichia coli (which we all have living inside us) has more than thirty different systems for sensing such things as oxygen, light, pressure, kinds of food, and what other species of organisms are nearby, and the ability to act accordingly. And it has short-term and long-term memory. Having such faculties, at any degree of complexity or sophistication, amounts to intelligence. Some arbitrary degree of intelligence might be chosen as the beginning of life.

Could the beginning of consciousness be the deciding stage? Consciousness can be distinguished from intelligence, with things like computers being intelligent but not conscious. Consciousness often but not necessarily includes the ability to feel pain and emotions. And, just as there can be grades of intelligence, there seem to be grades and types of consciousness. And this relates to the issue of when a mind begins. But a large part of the intelligence of a brain relates to things other than consciousness. There is no way of detecting when a developing brain begins to produce consciousness as distinct from having unconscious reactions.


Alternatively, could a new human life be considered to be established when it is equivalent to the intelligence or capability of an adult member of some other species, or of a particular computer?


The stage of development that requires consideration from the point of view of morality may not be the beginning of a new life but the beginning of being aware and able to feel pain. The ability to feel pain and have other kinds of sensory experience depends on a nervous system that provides information to the brain. In human beings, consciousness appears to be entirely dependent on the conditions in the brain, as is demonstrated by the functions of the brain’s neurotransmitters, by introduced chemicals such as analgesics, anaesthetics and hallucinogens, and by the various other ways of manipulating specific areas of the brain. (This is discussed further in Chapter 9 The Hard Problem of Consciousness.)

We assume people than ourselves are conscious by comparison with our own feelings and their actions. We attribute consciousness to other species according to their behaviour and its correlation with our own, and to the structure of their brains and nervous systems. So if these assumptions are correct, then the degree of development of the brain and nervous system determines the degree of consciousness in developing organisms. The stage may be reached some day when it is possible to determine whether a developing human foetus has reached the ability to experience pain.

This aspect of development would make virtually all of the species of animal that we eat more worthy of moral consideration than a human embryo or an early foetus.

If stage of development is to be a criterion for deciding when a life begins, it implies a gradation between being alive and having a life – that a particular, arbitrary, degree of being alive is necessary before a new life begins.

(After I had delivered the talk from which this chapter is derived, one member of the audience suggested that a human life would begin at the age of about nine or ten years. The rationale for this was that by that age the child begins to be able to act responsibly as a member of a family and of society. While I appreciate the logic of this idea, I think children clearly have a life  much earlier than this.)


Degree of Being Alive

We usually think of bacteria as being very much less alive than most animals. Individual cells of multicellular organisms must be even less alive than bacteria, even though they grow, divide, self-destruct and also perform the specific functions of the organ they are part of. But they have lost some of the functions that single cell organisms need to survive independently.

When someone dies, although the complex organic whole is dead, many of the organs, limbs and cells are still alive, and can be kept alive for some little time. These body parts would be considered to have a lower degree of life than a bacterium, which would be hunting for food and avoiding predators. A newly fertilized egg (or a virgin egg for species where fertilisation is not always necessary) is no more an individual life than a freshly amputated organ or limb. It is entirely dependent on the actions of a nurturing environment to begin its process of dividing and growing.

It could be argued that while an egg may have a similar degree of life to an organ ready for transplant, it has more potential. But as genetic technology continues to advance, any living cell might be potentially developed into a living organism. Cloning of non-human animals, using the nucleus of a body cell and an egg whose nucleus has been removed, was a step towards this. And induced stem cells have already been used to produce clones. So I do not think the potential of a fertilised egg gives it any special claim to being alive until some time after it starts the process of cell division.

The crucial question is how to assess the degree of life as it increases during the process from fertilised egg to adult, and to make a choice from that assessment. I don’t know of any objective way of measuring a degree of being alive other than the criteria already discussed. If there is a life force that pervades all things, then a measure of the complexity of an organism might be also a measure of this force, and a proxy measure of the organism’s degree of being alive. But this criterion, like the others, does not give a clear answer.

Nor do any of the other proposed biological criteria. But I think that, biologically, a life must begin some time after conception.

If the time of conception were to be the answer, then the technology of artificial cloning could pose a problem in deciding when this occurs. Artificial cloning involves the insertion of the nucleus of a body cell into an unfertilised egg that has had its nucleus removed. When this egg starts dividing it is implanted into the uterus of a host mother. Deciding the time of conception would be controversial if it were a human that was being cloned, particularly if after the egg started to divide some new cells were split off and separately implanted.

In some societies where infanticide was practised as a means of population control, the status of a newborn baby did not yet make killing it a moral issue. This may have been influenced by a decision that a newborn baby is still not sufficiently alive.

Just as there is a gradation in the degree of life, of intelligence and of sentience from the newly fertilised ovum to the living baby, so also is there a similar gradation of these faculties from the simplest microorganism to the human being. So it would be logical to give adult members of different species the equivalent moral standing to that of a developing human being – and vice versa. It might be argued that only human beings posses a soul, and because of that they should not be compared with other species. This argument depends on three assumptions: human beings have souls; no members of other species have souls; and having a soul is necessary for any organism to have an entitlement to be treated with compassion. I do not think there is any evidence to support, or refute, any of these assumptions. (If none of them were true, only non-human organisms would have souls, but it would be hard to say what benefit that would give them.) But this is not a biological argument.


Any moral judgment about the beginning of life made on biological grounds must necessarily be arbitrary. And it must be arbitrary irrespective of whether it is made rationally or emotionally. And the rational judgment will often differ from the emotional judgment.

If the reason for making a choice is to enable a decision about issues of morality, the choice will be influenced by pre-existing beliefs. This may seem unsatisfactory as an answer: it just shifts the question. But I think the foregoing arguments have shown that the concept of a life is unable to be sharply defined. So the idea of a precise moment of a biological beginning is meaningless. Also, some of these criteria would put the beginning at a time when a developing organism had acquired the ability to feel pain. And feeling pain might be the more significant moral issue. In fact, could there be there any other biological reason for wanting to define when a life begins?


Supernatural Criteria

The concept of life from a supernatural perspective is quite different from the biological description that was discussed at the beginning of this chapter and implied in the all the sections until this one. From a supernatural point of view life is some non-material essence that is closely associated with individual material organisms, but may also exist independently. This essence is the actual living entity: the body is just the material part of the organism that is energised by it. It follows from this that there is something very special about life, something sacred that must be treated with great respect. But since such respect seems to be granted mainly or entirely to humans but not to other species, it would seem that not all living species are considered, from this perspective, to have life.

The biological views of life are based on observation of the world around us. They accept the rigour of scientific method. Those who believe in the supernatural must rely on subjectivity – through intuition, or exercises of the mind such as meditation, or unsolicited revelation – or by reference to some source that is regarded to be authoritative. This does not in itself discredit belief in the existence of the supernatural nor its significance for life. All scientific observation must also contain a degree of subjectivity and trust in authoritative knowledge. Observation and the general unity of scientific knowledge offers a way of resolving differences of opinion. But there’s no apparent way of resolving differences of opinion about the supernatural.

If the supernatural, and not the body, is the living entity, then life begins when the supernatural (or, if you like, the soul) “enters the body”. If this is so, then presumably the physical entity is dispensable before the beginning and becomes sacred at the beginning. But there appears to be no reference in the foundation texts of the major religions concerning the stage of the development of the body at which this happens. However, different traditions have reached the conclusion that it is at conception, or on implantation of the embryo into the womb, or at some other specified time between conception and birth. These occasions are envisaged for humans only, but could be relevant to all placental mammals. Since they seem to rest on biological criteria, it is hard to see why the supernatural would distinguish between species. (The concept of the supernatural entering the body at the beginning of life and leaving the body upon death may be unduly materialistic, depending on whether the supernatural has dimensions of space and time and whether they mesh in with those of the material world.)

The beginning of life in non-human species may be an issue for reincarnation, where a particular supernatural might inhabit other animals as well as humans. Some people who do not believe in reincarnation think (some) animals, particularly their pets, have souls. So the beginning of the pet’s life may have some moral significance for this reason also. There is no agreement on this among believers in the supernatural.


All of this depends on the validity of the claim that life implies the presence of the supernatural. In Chapter 3 Monism and Dualism: A case for the existence of the supernatural and in Chapter 4 The Nature of the Supernatural I discussed this as one possibility that could not (yet) be ruled out as a justification of the existence of the supernatural. However, this justification of a supernatural entity would be seriously undermined, if not completely refuted, if it were ever to be demonstrated that an artificial organism made entirely of inorganic components could become alive. In the meantime I think the possibility still stands.

There are questions, however, about the relationship between the supernatural and organisms generally. Is it only Homo sapiens that requires the supernatural for it to be alive? If some, but not all, species require the supernatural, at what stage of evolution did it become necessary, and what criteria determined this? If it is all species, this would include bacteria and archaea. If it is only Homo sapiens, there must have been a crucial moment during the transition from, say, an advanced form of Homo ergaster to a primitive Homo sapiens. (Would this have been good luck or bad luck for the ones that didn’t quite make it?)

These questions must arise when comparing the status of human foetuses, and even of some infants, with that of adults of other species. Some people would dismiss this by denying the validity of evolution, perhaps attributing the existence of all members of all species to intelligent design (ID). In Chapter 7 Intelligent Design as a Scientific Theory I think I have demonstrated convincingly that there is no evidence to refute evolution and no evidence to support ID. But if ID were true, then even bacteria and other microorganisms would have souls, so the issue of comparative status remains. There is no agreement on these issues among believers in the supernatural.



There is no unambiguous way of deciding what life is. Life occurs in many forms, and changes continuously at all its levels of complexity. There is a difference between life as the particular condition of a piece of living material, and a life as a coherent individual living entity. But where is the dividing line between the two, and when does an individual life begin? This discussion has suggested the following possible answers:

All life on Earth is one biological entity that began billions of years ago. Parts of it are continually dividing, associating, separating and dying. New organisms are not new lives but new arrangements of living material.

All life consists of living cells, which may exist either separately or in a range of associations with other cells. The life of a single cell prokaryote organism begins at the completion of division of its parent organism. The beginning of the life of a complex organism, including a human being, depends on either how many cells you think are necessary (in the case of embryos), or what degree of coherence or complexity or size you think is necessary for the association itself to operate as a coherent entity.

As a multicellular organism grows, it develops varying degrees of mobility, intelligence, consciousness and independence. Its life may be thought to begin at some arbitrary stage of development of these faculties.

Biological considerations suggest that the beginning of a life is some time after conception.

The concept of a biological beginning point of a life is meaningless, because of the very complex and fluid nature of life itself. The concept may, however, be useful or even necessary for some purposes of human society.

Each life begins when the development of an organism is sufficient for the supernatural to enter it, whenever that may happen to be.

Life is essentially supernatural not biological. The supernatural determines when a life begins. We may have only subjective ways of knowing when this occurs.

All purported lives are just parts of a single all-encompassing supernatural.


Any of these might be relevant to issues such as methods of contraception, abortion, choice between saving an unborn baby or its mother, some aspects of biological research, and drowning newborn kittens. (Other considerations may also apply to such issues.)

I know of no way of demonstrating which of these answers are valid or invalid. Whichever you pick will depend on your religious and other beliefs, and on why you want a decision.