Causal Narratives
Constructing a causal model is telling your readers a story—the story of how a particular problem developed. Most problems in the real world are complicated, with multiple contributing factors, and your goal is to make (clear, useful, and persuasive) sense of that history for your readers. In addition to aiding the readers’ understanding, a causal model can serve as the set-up for a proposal by identifying the contributing factors that can be eliminated or changed to resolve (or at least alleviate) the problem.
Single Cause
In some situations, you may want to say to your readers, “This is what did it. This is the single cause.” In that case, you would need to examine each presumed or potential contributing factor and dismiss every other one, explaining why it could not have contributed to this problem. Be careful, though—most problems have multiple contributing factors, and the reader would only need to identify one other to undermine your argument.
Assigning Responsibility
In some cases, the purpose of your causal model might be to assign blame. If there is only one person responsible, such a model would be constructed similarly to the “Single Cause” Model—eliminate the groups and individuals who didn’t contribute to the problem, and then address the one who did. In other cases, however, you may need to divide the blame among various groups or individuals, assessing how much each party contributed and in what ways.
Reciprocal Causes
Sometimes causal relations are cyclic rather than linear: A causes B, which causes A, which causes B, and so on. For example, depression may lead a person to alcohol as a coping mechanism. But alcohol is a depressant, and alcoholism can certainly exacerbate depression, which leads to more drinking. In cases of reciprocal causes, the challenge is often figuring out where and how it would be best to try to break the cycle.
Chain of Events
A chain of events is like a row of dominoes. One thing causes another, which causes a third, which causes a fourth, eventually leading to the effect you are most interested in. Explaining a serial chain of events is useful in explaining how a very distant event (in time or space) played a role in bringing about a local effect.
Contributing Factors Working Together
Sometimes one factor is insufficient to bring about the effect in question. In order to demonstrate its role, you may need to document a collection of contributing factors, each inadequate by itself, but which when combined by circumstances are able to create the effect.
The Trigger
The Trigger narrative describes the existing conditions that allow an effect to come about, then names the precipitating cause that, given those conditions, results in the effect. It may also identify influences, those conditions that affect the progress of the result after the fact.
Absence of a Blocking Agent
Sometimes your point is that nothing exists to stop the problem, or that something hasn’t been done that should have been. In such a case, you may need to rely on analogy to a similar situation to show how such a blocking agent might have worked (or might work in the future).