“Bake, bake, bake a cake
The baker called us to him.
If you want to bake a cake,
Seven things are what you need:
Sugar and salt,
Eggs and lard,
Milk and flour,
and saffron makes it yellow”

(German children’s rhyme)

This rhyme is – in Germany, at least – the constant companion of small children making “cakes” in the sandbox. Often they are eager to try out the recipe in the kitchen, but the results are generally disappointing and the experience frustrating. What comes out of the oven does not satisfy even the indiscriminate taste buds of a small child. There is imminent danger that they will opt for the comfort of fast food permanently. But of course not all little cooks are put off. Some soon find more detailed recipes which promise better results. And there is no shortage of cookery and baking books with exact recipes and mouth-watering glossy photos. But even then success is not guaranteed. The devil is in the detail. What does “at medium temperature” mean? How big should the three eggs be, how soft the butter, and how long should the egg yolk be beaten with the sugar? The smallest variations can lead to big effects.

This is the key message with respect to the behavior of complex systems as it is also presented by the famous analogy of the butterfly in the Amazon rainforest beating its wings and causing a hurricane in the Gulf of Mexico. This was the example described by the meteorologist Edward Lorenz at the beginning of the 1960s. But while the good scientist may have exaggerated a little – or perhaps even a lot – the message is clear: minimal variations can have big effects. Moreover, these variations cannot be avoided – neither in theory nor in practice. Calculations made by a computer have a limited number of decimal places. This minimal inaccuracy is multiplied over the course of further processing and may end up in chaos. We cannot calculate everything that has to be controlled. In our everyday lives, we often do not have exact knowledge of the conditions which we have to deal with. The size of the eggs, the exact temperature in the oven, and the quality of the lobster can be determined only to a limited extent. These inaccuracies are what lead to surprises in the kitchen – not always, but regrettably often.

The crux of the matter is that the dynamics of complex systems cannot be calculated, nor can the development of their behavior be predicted. Planning in complex systems is very limited. It is not possible to predict the effects of actions which must be taken. The paradox of planning is that the knowledge needed for the planning does not become available until everything has been done, and then it is often too late. As a result, planning becomes a social ritual which serves no purpose other than to relieve the planners of responsibility for the effects of their actions – as long as they act according to the best of their knowledge and beliefs, they are not blamed if something goes wrong anyway.  

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