Effective strategic thinking is often possible only if we can grasp non-linearity in systemic relationships between causes and their effects. Yet, while we can usually see linear relationships without any problem, our minds persistently fail to grasp non-linearity.
In linear systems, actions have proportional effects, meaning we can easily see that if a little of some action does a little good, then slightly more of it will do slightly more good, and a lot of it will do a lot of good. In non-linear systems, on the other hand, an input produces disproportional output.
One example of non-linearity is curvilinear relationship: a small dose has a small effect, a slightly larger dose has an enormously large effect, and an even larger dose has no effect at all or a negative effect. Or the effect could be synergistic; for instance, a pesticide X may have a very low potency (e.g. 1 on 100-point scale) and a pesticide Y may also have similarly low potency, but together combined they may become hundred times more potent than each of them is by itself.