A title this would be, had I the originality.

Laundry aside, few of us have any problem distinguishing most things we see each day into separate "alive" and "not-alive" camps.

This is generally seen as a binary choice, and from a religious point of view, which camp something is in can be critically important.

But, like humanity, Life and death are not absolutes.

Health workers know this as a matter of course: ask anyone who has spent fifteen minutes pumping away at someone's chest in CPR, only to declare the patient dead, whether there was a definitive moment of death. There is not, any more than there is a definitive moment where the machines change from keeping an alive person from dying, to keeping a dead person from rotting. There are just arbitrary guidelines, which change as we get better at restoring people from the grey areas.

As there is often no definitive end to an individual life, so there is no definitive beginning. This becomes very political around the issue of abortion. The majority of people who believe that there is a black-and-white state of life or non-life define the beginning of an individual's life as one of birth, viability (where the baby could survive without the mother), or conception (when the egg is fertilised: the Vatican's choice).

Thought experiment for birth: Births can be induced at any time from conception onwards. The only difference between one that survives or not is the viability. How does "life begins at birth" differ from "life begins at viability"?

Thought experiment for viability: Which instant of time is it, at which a second either way means the difference between life and death? The point in time keeps shifting as we get better medical technology. Once someone finds a way to bring a fertilised egg all the way to birth in an artificial womb, so that every fertilised egg is "viable", what will the difference be between this and the conception argument?

Thought experiment for conception: we could create people (eg by splitting a blastocyst to create identical twins) without a moment of conception: these are, most would agree, still human people. Equally, parthogenicaly-born lizards are still considered lizards, even though they have no father.

As there is often no definitive beginning or end to a life, so there is no definitive boundary.

Thought experiment: are twins separate people? If yes, are conjoined twins two people? If yes, then is a four-legged man with one head two people, or one? At some point, you place the division between "one being" and "two beings". At that point, separating them more or less by a single cell will change their nature from single to dual. What happens if that cell is there, but dies? Does a life die with that cell? What happens if it is not there, and grows? Is a life created with that cell?

So, we've established that the life of an individual needn't necessarily have a clear beginning or end. Individuality itself is a concept with fuzzy boundaries.

What is life?

Some believe life is magic from the Gods. And fair enough to them, I can't argue with that. But now it's here, life seems to be some kind of continuous process of growth and reproduction. Something is alive if it's involved in that process.

People have carefully mapped the processes of living things, and claim these are necessary, if not sufficient, for something to be classed as living.

Respiration, Synthesis and transport of metabolites, Nutrition: is a person starving to death or suffocating already dead? Is a mayfly dead?

Environmental response

Locomotion: is a tree dead once it is planted?

Growth: is an organism shrinking during hibernation not alive?

Excretion: is an organism which stores its waste products dead?

Reproduction: Is a mule dead?

They don't look that necessary for something to be alive, though they may all ultimately be necessary for successfully passing your genes on to the next generation.

They are certainly not sufficient to define life: if they were then an automated factory that creates automated vehicles that automatically build factories would be "alive".

Is a bacterium alive? A virus? What is the minimum physical thing that can be said to be a marker for "life"? What is the minimum involvement in the process we call life, that can be said to be "alive"?

If we define that point, and then make a machine that has that property, is it "alive"?

I feel that life is a process that started millions upon millions of years ago; the idea of an individual life starting and stopping is a convenient simplification for our daily use; but that abortion is more complex.

So "alive" = "participating in the process of life". Circular definition, I know.

A sperm or egg growing inside someone - part of a living being? Up until some point, yes, it has to be. The cell has to split off an existing cell, and that cell is part of someone.

A detached sperm - alive? Yes.

A detached egg - alive? Yes.

A fertilised egg, then, is two individual, combining to make one. Nothing *starts* there - it only continues the processes begun by the egg and the sperm. Which are continuing the processes begun by the cells that bore them, and so on back for millions of years.

The fact that they occasionally form into globs of cells called people is not terribly relevant, to Life's point of view.