"Why?" may be the question most commonly asked by human beings. We are fascinated by the reasons for everything we experience in life. We ask questions about natural phenomena: Why is the sky blue? Why does a teakettle whistle? Why do some materials act as superconductors? We also find human attitudes and behavior intriguing: Why is chocolate so popular? Why do some people hit small leather balls with big sticks and then run around a field stomping on little white pillows? Why are America's farms economically depressed? Why did the United States go to war in Vietnam?
Explaining why something occurs can be the most fascinating — and difficult — kind of expository writing. Answering the question "why" usually requires analyzing cause-and-effect relationships, but the causes maybe too complex or intangible to identify precisely. We are on comparatively secure ground when we ask why about physical phenomena than can be weighed, measured, and replicated under laboratory conditions. Under those conditions, we can determine cause and effect with precision. Fire, for example, has three necessary and sufficient causes: combustible material, oxygen, and ignition temperature. Without each of these causes, fire will not occur (each cause is "necessary"); these three causes are, taken together, enough to cause fire (all three are "sufficient"). The cause-and-effect relationship, in this case, can be illustrated by an equation:
- cause 1: combustible substance
- cause 2: oxygen
- cause 3: ignition temperature
- effect: fire
Analyzing both necessary and sufficient causes is essential to explaining an effect. You may say, for example, that wind shear (an abrupt downdraft in a storm) "caused" an airplane crash. In fact, wind shear may have helped cause the crash (been necessary), but by itself wind shear was not the total (sufficient) cause of the crash: An airplane with enough power may be able to overcome wind shear forces in certain circumstances. An explanation of the crash is not complete until you analyze the full range of necessary and sufficient causes, which may include wind shear, lack of power, mechanical failure, and even pilot error.
Sometimes, explanations for physical phenomena are beyond our analytical powers. Astrophysicists, for example, have good theoretical reasons for believing that black holes cause gigantic gravitational whirlpools in outer space, but they have difficulty explaining why black holes exist — or whether they exist at all.
In the realm of human cause and effect, determining causes and effects can be as tricky as explaining why black holes exist. Why do some children learn math easily, while others fail? What effect does failing at math have on a child? What are necessary and sufficient causes for divorce? What are the effects of divorce on parents and children? You may not be able to explain all the causes or effects of something, but you should not be satisfied until you have considered a wide range of possible causes and effects. Even then, you need to qualify or modify your statements, using such words as might," "Usually," "often," "seldom," "many," or "most," and then giving as much support and evidence as you can.
