The life of a human being cannot be totally described or defined by the detailed analysis of all the activities that are necessary for life. It is rather the sum of these activities co-ordinated in a delicate and beautiful way to form a unitary phenomenon which we call human life. Since the organisation of the human body is so complex, it is easily damaged, although damage can sometimes be repaired. The testing of nuclear weapons causes damage to life which cannot be repaired, and which poses special moral problems because future generations are also affected.

The final executor of the coordination of the human body is the nervous system, organising all the physical activities of the different parts of the body, organising many chemical activities, such as the secretion of chemicals from the glands, and finally creating and organising the intellectual and emotional activities of the brain.

And yet the nervous system is itself coordinating a series of already delicately organised systems. Each organ in the body, be it the liver, a muscle, or the intestine, is itself a finely balanced system of many millions of cells acting in concert to produce the unitary function and nature of the organ itself.

Finally, at the deepest level of analysis, each cell is a unit produced by the coordination of reactions between the complex ‘organic’ chemicals which alone are capable of reacting in such delicate and organised systems. The total activity of every cell in the body is controlled, organised and balanced by the contents of a single tiny body present in each cell. This tiny body is called the nucleus. Since the cell is the smallest dynamically organised unit in the total organisation of the body, the organisation of the cell is the most fundamental activity in the life process.

The adult human body is produced only after a long period of development, taking about 20 years. From birth onwards development is comparatively slow, but the new born baby develops in only nine months from a single cell, the fertilised egg, formed by the fusion of sperm and ovum. The responsibility of initiating the marvellously complex processes which lead to the formation of the adult human being rests entirely on this single cell. Furthermore, the total potential for the whole developmental process is present in the fertilised egg. The pattern development will take, and its consequences, the final form and nature of the adult produced, are decided by factors present in the nucleus of the fertilised egg. These factors, of which there are probably tens of thousands, are called genes, and are positioned along the length of a number of threadlike objects, the chromosomes. In the nucleus of the fertilised egg of the human being there are 46 chromosomes, 23 of which come from each parent in the sperm and ovum, so that the child shares the heredity of both parents.