Reasoning from Evidence resembles the scientific method. You gather evidence, examine it and draw conclusion. Here’s fairly typical example in which a writer cites statistics and then theorizes about what they mean;
Japan’s population is aging more rapidly than any on the plant – by 2015 one in four Japanese will be elderly The birthrate has sunk on 1.34 per woman, well below replacement levels [The birthrate in the United States by contrast, 2.08.) Last year Japan dropped from the eighth largest nation in the world to the ninth. The smallest class in recorded history just entered elementary school. Demographers predict that within two decades the shrinking labor force will make pension taxes and health care costs untenable, not to mention that there will not be enough workers to provide basic services for the elderly. There are whispers that to avoid ruin, Japan may have to do the unthinkable. Encourage mass immigration, changing the very notion of what it meant to be Japanese. ( Peggy Orenstein : PARASITES IN PRÊT – A – PORTER
You can use this pattern in two ways. You can give the evidence first and then generalize from it as the preceding passage does or you can state your main point first and then present the evidence as the following example does.
As absorbed as society seems to be with alcohol, most people know shockingly little about alcoholism. Here’s disease that affects between 5 and 10 percent of the population. It causes half of all violent deaths, from accident, suicides and homicides, triggers fatal diseases raining from cancer to cirrhosis and costs Americans about $ 180 billion a year. Yet smart educated people don’t even accept that it’s disease or that it may be our most egregiously under treated epidemic. (JIM Atkinson : Sober
Keep three cautions in mind when you’re arguing from evidence.
• Give enough evidence to warrant your conclusion. If you make a claim on the basis of only a few examples, you will damage your credibility.
• Be sure your sample is representative and takes data from a range of evidence. You don’t want to look as if you’re stacking the deck.
• Be sure your facts are accurate and cite your sources to show where you got them.
Remember also to highlight statistical evidence in a graph or chart when possible and to use lists to present several points. For suggestions, see Chapter 11 on document design