In his master work The City of God, the great Patristic bishop and theologian Augustine of Hippo argues that 'our will is for our welfare' and this results in acts of sin because, misled in our thinking because of the Fall, 'we commit sin to promote our welfare.'

I was reminded of Augustine's words recently when thinking about the justification that President Putin put forward for the Russian invasion of Ukraine. In his speech at the Victory Day parade in Moscow on 9 May, and on several other occasions, Putin has declared that his invasion of the Ukraine was justified because the Ukrainians are Nazis who were planning an attack on Russia in league with NATO. It follows that the welfare of the Russian people requires the 'de-Nazification' of Ukraine and the purpose of the Russian 'special military operation' is, hence, to achieve this end.

This argument is a classic example of what Augustine is talking about. There is no reason to doubt that Putin does seek the welfare of the Russian people, but tragically his particular brand of political paranoia has led him to believe that the Western world is aiming to destroy Russia using Ukraine as its tool. This mistaken understanding of the world has then led him to act in an ethically unacceptable fashion by attacking Ukraine, an act which in Christian terms violates the commands against coveting, theft and murder in the Ten Commandments – coveting because he desired to own someone else's country, theft because he engaged in armed robbery to try to fulfil this desire, and murder because this has resulted in death and injury to countless Ukrainians (and Russians as well).

All this highlights a key principle for Christian ethics, which is that if we are to avoid the sort of unethical activity exemplified by Putin, we have to learn to understand the world rightly. Right ethical action flows from right understanding, which in turn flows from a careful study of the Bible and the world in which we live, and which God has made and (what has been described as the 'two books' of Scripture and nature).

Accepting this principle helps us to take a right view not only of what is happening in Ukraine, but also helps us to take a right view of three other current issues, transgenderism, same-sex sexual relationships and abortion.

In the case of transgenderism, the issue is that transgender advocates are now increasingly arguing that there is no biological distinction between men and women. What transgender advocates desire is the social acceptance of transgender people and their identities, and to this end they contend that maleness and femaleness as traditionally understood has no objective biological basis. Thus, on 17 May the Head of Trans Inclusion at Stonewall declared in court, "Bodies are not inherently male or female. They are just their bodies."

This statement is theological and scientific nonsense. The Bible teaches - and science confirms - that God has created human beings as male and female (Genesis 1:27), and that what distinguishes men from women is that they have, from the moment of conception, bodies which are designed to play different roles in sexual reproduction and in the nurture of children once they have been born. It is because this is so that human beings can fulfil God's command to 'be fruitful and multiply' (Genesis 1:28). The Head of Trans Inclusion at Stonewall thus exists because bodies are in fact "inherently male and female".

Understanding the fact that God has made his human creatures male and female in this way forms the basis for a proper Christian ethical approach to the transgender issue. In the words of the Anglican ethicist Oliver O'Donovan, the proper Christian approach is to understand that:

"... we cannot and must not conceive of physical sexuality as a mere raw material with which we can construct a form of psychosexual self-expression which is determined only by the free impulse of our spirits. Responsibility in sexual development implies a responsibility to nature—to the ordered good of the bodily form which we have been given."

In specific terms this means that, from a Christian perspective, human beings are called to live as the male and female creatures God has made them to be (as determined by their bodies), however difficult this may be psychologically, and to do all they can to assist others who find it a particular struggle to live in this way to also live out their true male and female identity.

Understanding the creation of human beings as male and female creatures whose bodies are created to play a particular role in sexual reproduction, also provides the correct basis for a proper Christian understanding of the issue of same-sex sexual relationships. God has designed men and women to engage in sexual intercourse with members of the other sex (which is how sexual reproduction takes place).

It follows that same-sex sexual activity is, as Paul says in Romans 1:26-27, 'unnatural.' It is against the way that God created his human creatures to behave. It is this truth that underlies the various biblical texts that implicitly or explicitly reject gay and lesbian sexual activity and it is the reason why such activity has traditionally always been rejected by the Christian Church.

In addition, the Bible also teaches that God has created marriage between one man and one woman as the proper setting for sexual activity (Genesis 2:18-25) and as an image of the relationship between God and his people, both now and in eternity (Ephesians 5:31-32, Revelation 21:2). Understanding this further truth means that from a Christian perspective marriage needs to be between two people of the opposite sex and that a same-sex union, however loving, cannot properly be seen as a marriage at all.

Turning to the issue of abortion, an issue which has once again been in the headlines because of the recent leak of a draft opinion on this subject from the United States' Supreme Court, a proper approach to the matter has to be based on an understanding of when human life begins.

The testimony of the Bible in passages such as Job 31:15, Psalm 139:13-18, Isaiah 49:1 and Luke 1:41-43 is that human life begins in the womb. Modern scientific study concurs and adds that human life begins at the very moment of conception. As the American writer Nancy Pearcey notes, there is no 'magic moment' in which a foetus becomes a human being. Human life is a continuity from conception onwards. The argument that unborn children are not truly human because they lack sentience and autonomy only works if we then say (which most people rightly won't) that adult human beings are also not truly human if they lack sentience or autonomy for some reason.

What this understanding of the matter means is that the ethical debate about abortion cannot be properly framed simply in terms of the physical, psychological or economic wellbeing of the mother. These things are hugely important, but they have to be balanced against the right to life of the unborn child. To put it another way, the ethics of abortion are not just about the right of a woman 'to control her own body' as the pro-choice slogan goes; they are about whether she has the right to control the body of an unborn child to the extent of bringing his or her life to an end. President Biden recently gave the game away when he commented that the abortion debate was about the right 'to choose to abort a child'. Exactly so.

Viewing the matter in this way does not entail saying that all abortion is automatically ruled out. There are hard cases, such as when there is an ectopic pregnancy, or profound foetal abnormality, where it can be plausibly argued that bringing the life of an unborn child to an end is the ethically right thing to do. However, even in such cases it needs to be recognised that this is what has taken place. A human being has died, and their death needs to be acknowledged and their loss properly grieved.

The principle of ethical action flowing from right understanding does not make ethical decisions subjectively easier to make. Willing our welfare as fallen creatures in a fallen world means that we will always be tempted to make a decision because it feels right rather than because it is right. However, as we have seen in this article, when we make the effort to understand what is right, we are then in a position to choose to resist the pull of our fallen nature and to do the ethically right thing.

Martin Davie is a lay Anglican theologian and Associate Tutor in Doctrine at Wycliffe Hall, Oxford.