There are times when a simple, uncontestable fact is not as effective or persuasive as a step-wise chain of statements that lead to that fact. For example, if I told you that Clean, potable water was good, you’d certainly agree. After all, who doesn’t want clean water for drinking, bathing, and cooking? It’s an alloyed good. What I haven’t given you though is a reason that clean water is good or an argument you can make to others to convince them that clean water is good. On the other hand, if I present you with an extended chain of consequences, all leading from that fact, well, then I’ve cemented your agreement and provided you with the information to persuade others.
There are two principal kinds of explanatory chains; negative and positive.
A negative chain begins with a negative situation or outcome and then proceeds to back out the negative precursors that brought about that situation. Figure 1 is an example of a negative chain. It begins with a clear negative, in this case the fact that diarrhoeal diseases are the 2ndleading cause of death for young children. It then steps down the chain to show what causes that, ending with insufficient clean, or contaminated, water. So now, we have dirty water as the root cause of these diarrhoeal deaths, and by implication, a strong argument for clean water.
A petal diagram, like Figure 2, shows multiple negatives all pointing to the same root cause, making an even stronger case. In effect, such a petal diagram says that even if you doubt the importance of one negative outcome or question any of the chains’ links, there are now many other reasons to deal with that root cause.
In contrast, a positive chain starts with a situation or seed and shows what consequences spring from it. Figure 3 takes the negative chain from Figure 1, reverses it, and adds on five additional blocks. And whereas negative chains tend to have a fairly short number of steps, positive chains can be pretty much a long as you wish, with the understanding of course that the further out the chain you go, the smaller the direct effect of the seed. [ 4 ] That is, factors other than those directly in the chain also contribute to outcomes. For example, more years of school is not the only factor affecting teen pregnancy; availability of contraception, family income, and others also play a role.
And for positive chains, the opposite of a petal diagram is a tree diagram (not shown), with ever more branching as more effects are added, progressing up the chart.
Presenting a chain of either consequences (positive chains) or determinants (negative chains) doesn’t require a diagram, but such images do tend to make a strong case. It may just be that the arrows in such a diagram convey a certainty and inevitability that phrases like “tends to” or “leads to” simply do not.
So in words or diagrams, when you explain the chain, you bolster your argument and arm your reader to do likewise as they then explain it to others.
Please leave comments below.
[ 4 ] Indirectly, however, seeds can have an almost infinite effect; think of the butterfly effect in chaos theory.