You will find that in this topic there is a certain amount of overlap with another section A topic, death and life after death. In particular, the reasons for believing in a soul or in the afterlife are often similar. This topic is also relevant to the section B topic the meaning and purpose of life.
Your 'nature' refers to your character; what makes you, you. Everyone has their own specific character that is individual to them. However, most people would also say that there are things that are common to human beings in general, things that make us human. This is what we mean when we talk about human nature. When we investigate what people believe about 'human nature' we are looking at what it means to be human.
St Augustine's view on human nature has been very influential in shaping traditional Christian beliefs.
According to Augustine, human beings have two parts, a body and a soul. Both of these are necessary for us to be human and both are created by God. The soul is the rational and moral part whereas the body is more driven by instinct and physical drives. Augustine said that the soul should therefore guide the body (because it is rational so can make reasoned decisions). He used the analogy of a rider and a horse. The soul is like the rider steering the animal and the horse is like the body providing the impulses and carrying the soul.
Augustine said that since the Fall the body had become rebellious and often refused to obey the rational soul. He called this rebellion CONCUPISCENCE. When people sin they often go against their better judgement. I.e. they do wrong even though they know they should not. This is concupiscence in action!
In many respects Aquinas' view was similar to Augustine's. However, he puts a slightly more positive slant on human nature.
He believed that because everyone is created in God's image all people are essentially good. He believed that people never sin deliberately. He thought that the Fall damaged people's ability to use their reason correctly. This meant that when people are deciding how to behave they sometimes think something is the right course of action when it is not. They mistake an apparent good for a real good.
Not everyone believes in human nature. Sartre was a philosopher who argued that there is no such thing as human 'essence' or human nature. Who we are and what we are like comes from the choices we make and how we live our lives. This way of thinking led to a philosophy called existentialism.
Sartre is famous for saying 'existence preceeds essence' which means that your life and choices come first and make your nature - not the other way around.
The body is the physical, material part of a human being. In Genesis 2 God creates Adam out of the dust of the earth, that is, out of physical 'stuff'.
Jesus was Jewish and Christianity was born in the Jewish world. However, as Christianity spread it came into contact with Greek ideas. In the ancient Greek world the physical body was often regarded as something that dragged the soul down and distracted it from the pursuit of higher things. Christianity was partly influenced by this dualistic world view but it has a much more positive view of the body than traditional Greek thought. It is part of God's creation and the Bible says that 'your body is a temple of the Holy Spirit' (1 Corinthians 6:19) and those that destroy the body will themselves be destroyed. Jesus' resurrection was supposed to be physical rather than just spiritual and he invited his disciples to touch his wounds to prove that he was not just a ghost. Christians traditionally believe that life in the afterlife will involve body as well as soul although according to Paul the resurrected body will be different in that it will not be perishable. (See notes on death and life after death for Paul's discussion of what the resurrected body will be like).
Soul and Spirit:
The terms soul and spirit are more difficult to define and many Christians use them interchangeably.
However, the Bible implies that there is a discernible difference between the two. In 1 Thessalonians 5:23 spirit and soul are listed separately implying that they are different things; the writer asks 'may your whole spirit and soul and body be kept blameless'.
The English word 'soul' is used to translate the Old Testament Hebrew word 'nephesh' which means something like 'life force' or even just 'life'. In Genesis 2, when God breathes into Adam he becomes 'a living soul'. It is also used to translate the New Testament Greek word 'pscyhe' which is often used to mean character or personality. All living beings have a life force or character and animals are also described as having souls or as being living souls.
The word 'spirit' is used to translate the Hebrew word 'ru′ach' and the Greek word 'pneuma' and usually understood to be the non-material 'stuff' that also goes to make up human beings. The spirit is sometimes compared to the breath of God and this gives an indication of what the spirit is meant to be like - i.e. it has no physical substance. God's Holy Spirit is the power of God that is active in the world and both angels and God are generally believed by Christians to be purely spiritual beings (except when God is incarnate as Jesus when he obviously has a physical body as well).
So we can technically distinguish between spirit and soul. However, you don't need to worry about it too much. The Edexcel RS IGCSE definition of soul is 'the spiritual or non-material part of a person'. This definition combines the idea of the soul as life-force and the spirit as breath of God. The catechism of the Roman Catholic Church defines the soul as:
The main idea is that the spiritual soul, like the body, is essential for human beings. We would not be human if we had a body but no soul. Without the soul no life is possible. James 2:26 says 'the body apart from the spirit is dead'.
There is some indication in the Bible that the spirit has a sort of natural immortality. Ecclesiastes 12:7 says that at death 'The dust [i.e. body] returns to the earth just as it happened to be and the spirit itself returns to the true God who gave it'. The author of Matthew's gospel records Jesus' warning that you should 'not fear those who kill the body but cannot kill the soul. Rather fear him who can destroy both soul and body in hell.' (Matthew 10:28) which implies that human actions cannot destroy the soul although they can destroy the body.
The spirit, being non-material, obviously cannot decay in the way that material things can. Paul says that in the afterlife natural bodies will be replaced by spiritual bodies (see notes on death and life after death). If the spirit cannot decay, get ill or die then it seems natural that it would automatically survive death.
The Greeks like Plato thought that the soul is immortal and would return to the spiritual world of ideas once freed from the body that dragged it down and kept it prisoner in the material world. However, traditional Jewish thought (and remember Jesus was Jewish) did not really have a dualistic world view and the idea of an immortal soul was not really present. Living beings have a life force (soul) but this dies when they do.
Generally speaking, modern Christians do believe that the soul is naturally immortal.
Physicalists are people who believe that only physical things exist. In other words, they reject any belief in the spiritual elements of the world. Physicalists would say that none of the so called 'evidence' for the soul is convincing. It is anecdotal, subjective and hard to test. Often there are rational explanations which might seem more plausible than supernatural explanations.
For example, a physicalist might argue that things like religious experiences can be explained in terms of brain activity. There have been suggestions that certain types of temporal lobe epilepsy can produce religious experience-like sensations [report here]. Richard Dawkins and other biologists have explained that it is possible for altruistic behaviour to evolve as it benefits the species as a whole [report here]. Altruism is the basis for morality so morality does not need the soul to explain it either.
Physicalists might use Ockham's razor to argue that natural and physical explanations are more likely to be correct than supernatural and spiritual ones.
To summarise the physicalists view point we can say: