So far I’ve been discussing implicit metaphors, but explicit metaphors can also lead us astray without us realizing it. We use one thing to metaphorically stand in for another because they share some important property, but then we assume that additional properties of the first thing must also be shared by the second thing. For example, here’s a scientist explaining why complex organisms were traditionally assumed to be more vulnerable to genetic mutations, compared to simpler organisms: “Think of a hammer and a microscope… One is complex, one is simple. If you change the length of an arbitrary component of the system by an inch, for example, you’re more likely to break the microscope than the hammer.”
That’s true, but the vulnerable complexity of a microscope isn’t the only kind of complexity. Some systems become more robust to failure as they become more complex, because of the redundancies that accrue — if one part fails, there are others to compensate. Power grids, for example, are built with more power lines than strictly necessary, so that if one line breaks or becomes overloaded, the power gets rerouted through other lines. Vulnerability isn’t a function of complexity per se, but of redundancy. And just because an organism and a microscope are both complex, doesn’t mean the organism shares the microscope’s low redundancy.