Craving is a fire which burns in all beings: every activity is motivated by desire. They range from the simple physical desire of animals to the complex and often artificially stimulated desires of civilised people. To satisfy desire, animals prey upon one another, and human beings fight, kill, cheat, lie and perform various forms of unwholesome deeds. Craving is a powerful mental force present in all forms of life, and is the chief cause of the ills in life. It is this craving that leads to repeated births in the cycle of existence.
Once we have realised the cause of suffering, we are in a position to put an end to suffering. So, how do we put an end to suffering? Eliminate it at its root by the removal of craving in the mind. This is the Third Noble Truth. The state where craving ceases is known as Nirvana. The word Nirvana is composed of ‘ni’ and ‘vana ’, meaning the departure from or end of craving. This is a state which is free from suffering and rounds of rebirth. This is a state which is not subjected to the laws of birth, decay and death. This state is so sublime that no human language can express it. Nirvana is Unborn, Unoriginated, Uncreated, Unformed. If there were not this Unborn, this Unoriginated, this Uncreated, this Unformed, then escape from the conditioned world is not possible. Nirvana is beyond logic and reasoning. We may engage in highly speculative discussions regarding Nirvana or ultimate reality, but this is not the way to really understand it. To understand and realise the truth of Nirvana, it is necessary for us to walk the Eightfold Path, and to train and purify ourselves with diligence and patience. Through spiritual development and maturity, we will be able to realise the Third Noble Truth. But first we must begin with sraddha, the confidence or faith that the Buddha is truly competent to lead the way. The Noble Eightfold Path is the Fourth Noble Truth which leads to Nirvana. It is a way of life consisting of eight factors. By walking on this Path, it will be possible for us to see an end to suffering. Because Buddhism is a logical and consistent teaching embracing every aspect of life, this noble Path also serves as the finest possible code for leading a happy life. Its practice brings benefits to oneself and others, and it is not a Path to be practised by those who call themselves Buddhists alone, but by each and every understanding person, irrespective of his or her religious beliefs.
(From Walpola Rahula, What the Buddha Taught)