The prohibition of the taking of human life is deeply rooted in Christian faith. It is one of the fundamental prohibitions in the Old Testament.

Whoever sheds man’s blood,
By man his blood shall be shed;
For in the image of God
He made man.

Genesis 9:6 (NKJV)

Or Exodus 20:13 (NKJV)

“You shall not murder”

It is presupposed by Jesus (New Testament).

Matthew 5:21

“You have heard that it was said to those of old, ‘You shall not murder, and whoever murders will be in danger of the judgment.”

Romans 13:9-10

⁹For the commandments, “You shall not commit adultery,” “You shall not murder,” “You shall not steal,” “You shall not bear false witness,” “You shall not covet,” and if there is any other commandment, are all summed up in this saying, namely, “You shall love your neighbour as yourself.”
¹⁰Love does no harm to a neighbour; therefore, love is the fulfillment of the law.

From these and other passages it is easy to trace a number of reasons for this prohibition. Human life is created by God, but more than that, it is created in his image.
God loves his people, and commands them to love one another.

Jesus Christ is the Word made flesh, and more than that, he died to bring life to the world.
How can we kill another human being for whom Christ also died?

The matter is summarised in the command to love our neighbour (Romans 13:10)

These themes provide the basis for the sanctity of human life and there are others relevant for some borderline cases.

The question arises whether there are any permitted exceptions? That is to say are there any occasions when human life may be taken, and if so, on what grounds?

Although modern translations of the Ten Commandments vary (some using ‘murder’, some ‘kill’), there can be no reasonable doubt about what is intended.

Exodus 20:1-17

¹And God spoke all these words, saying:

²“I am the Lord your God, who brought you out of the land of Egypt, out of the house of bondage.

³“You shall have no other gods before Me.

⁴“You shall not make for yourself a carved image, any likeness of anything that is in heaven above, or that is in the earth beneath, or that is in the water under the earth;

⁵you shall not bow down to them nor serve them. For I, the Lord your God, am a jealous God, visiting the iniquity of the fathers upon the children to the third and fourth generations of those who hate Me,

⁶but showing mercy to thousands, to those who love Me and keep My commandments.

⁷“You shall not take the name of the Lord your God in vain, for the Lord will not hold him guiltless who takes His name in vain.

⁸“Remember the Sabbath day, to keep it holy.

⁹Six days you shall labour and do all your work,

¹⁰but the seventh day is the Sabbath of the Lord your God. In it you shall do no work: you, nor your son, nor your daughter, nor your male servant, nor your female servant, nor your cattle, nor your stranger who is within your gates.

¹¹For in six days the Lord made the heavens and the earth, the sea, and all that is in them, and rested the seventh day. Therefore, the Lord blessed the Sabbath day and hallowed it.

¹²“Honor your father and your mother, that your days may be long upon the land which the Lord your God is giving you.

¹³“You shall not murder.

¹⁴“You shall not commit adultery.

¹⁵“You shall not steal.

¹⁶“You shall not bear false witness against your neighbour.

¹⁷“You shall not covet your neighbour’s house; you shall not covet your neighbour’s wife, nor his male servant, nor his female servant, nor his ox, nor his donkey, nor anything that is your neighbour’s.”

The Old Testament clearly intends that some taking of human life is in fact required, for instance in punishment of the murderer,

Genesis 9:6

“Whoever sheds man’s blood,
By man his blood shall be shed;
For in the image of God
He made man.

And also the Adulterer.

Leviticus 20:10

‘The man who commits adultery with another man’s wife, he who commits adultery with his neighbour’s wife, the adulterer and the adulteress, shall surely be put to death.

Genesis 9:6 offers us a strong clue for considering how we should approach the possible exceptions.

The murderer’s life is taken precisely because he has shed the blood of another. Killing is here required in order to defend the living and to protect the sanctity of human life.
This strongly suggests the fundamental reason which can alone justify deliberate killing, namely, the protection of other lives.

The Old Testament thus underwrites the sanctity of human life and provides ground for the taking of life in defence of that sanctity.
This is paradoxical, but it is not self-contradictory.

The New Testament, however, provides even more cogent grounds for not taking human life.

Christ lived in human form and died to save humanity. How then can Christians ever kill?
There have always been those who argue that Christians should never shed the blood of another, not even to uphold the law, defend one’s country, or defend one’s own life.

The seriousness of the crime of murder or homicide cannot be in question.
Murder is the unlawful and deliberate killing of another.

Killings commanded or authorised by the State, such as those in war, or in law enforcement, are not necessarily murder.

Unlawful killings are murderous if done with deliberate intention.

Deliberately causing serious injury which leads to death is also murder.

This excludes killing by accident and killing where it is not possible to ascribe a full degree of responsibility.

Killing in self-defence is not usually murder; and there is a special category for the killing of babies in utero (Abortion), and in some circumstances for the killing of infants (Infanticide).

In Australian law there is no special category for ‘mercy-killings’ (or Euthanasia).

The legal distinctions rest on moral grounds. The grounds for the possible lawfulness of killing are close to the grounds for moral justification.

The basic Christian moral argument is that it may, in some circumstances, be both justified and a duty to take one life in order to save another.
This can happen only where the life to be taken directly threatens the life of the other.

The reasoning is clear in the case of ectopic pregnancy (a condition in which the growth of the foetus seriously jeopardises the health of the mother).
A different example is provided when a policeman has no alternative but to shoot a gunman in order to prevent him killing others.

The logic of this example is easily extended to cover killing in warfare. A similar but not identical argument may support the case for capital punishment (in continuity with Genesis 9:6).

An argument which I do not subscribe to because the sanctity of life can be best respected and protected by other less final forms of punishment and because the distinction between deliberate and unintentional killing is also essential.

A death brought about by accident may still be culpable, if there was a lack of care or forethought (maybe, in a road accident). But the responsibility is a different one.

Justifiable killing must be indirect (not directly willed and intended).

In the examples in the previous paragraph, the surgeon’s direct intention is to save the mother’s life, the policeman’s action to save the lives of the people threatened by the gunman.
In both cases the deaths are willed only indirectly (Double Effect).

In the debate about what is directly intended, and what indirectly, it is important to distinguish between motive and intention.
The motive refers widely to the general context of action, the intention to what is directly and actually done.

This can be summarised by saying that for certain categories of morally grave actions, for example, causing the death of a human being, the principle of double effect combines the claim that it can be morally permissible to cause a death incidentally as a side effect of pursuing a good end with a general prohibition on causing the death of an innocent human being for the sake of a good end.

The prohibition is absolute in many Christian applications of the principle.

I propose four conditions for the application of the principle of double effect:

1. The act itself must be morally good or at least indifferent.

2. The agent may not positively will the bad effect but may permit it. If he could attain the good effect without the bad effect, he should do so. The bad effect is sometimes said to be indirectly voluntary.

3. The good effect must flow from the action at least as immediately (in the order of causality, though not necessarily in the order of time) as the bad effect. In other words, the good effect must be produced directly by the action, not by the bad effect. Otherwise, the agent would be using a bad means to a good end, which is never allowed.

4. The good effect must be sufficiently desirable to compensate for the allowing of the bad effect.

For clarification of the fourth “proportionality” condition, here are five different dimensions of assessment that could be used.

1. the degree of badness of the effect

2. the degree of dependence of the bad effect on the act

3. the proximity of the effect to the bad act

4. the degree of certainty that the bad effect will occur and

5. the degree of obligation to prevent the bad act.