Now put four magnets in a square under the pendulum. The effect of such a cause can not be predicted in detail, but the pattern of the effects of several identic causes can be analysed using statistics and chaos theory. An example for this is radioactive decay. You can't say in what given moment a certain atom will disintegrate, but because there are so many atoms you can statistically say that in a given amount of time, so and so many atoms will have disintegrated. However, you can never say for certainity exactly how many atoms have disintegrated in a finite time period.
Complex systems give rise to new levels of organisation.
Take, for example, a picture in a newspaper. It consists of simple dots. One can not see the picture by observing the dots one at a time, to do so you must step back and look at the whole picture. Or take the words in this document. They are built on letters, but from analyzing the letters alone, one at a time, you can't get any understanding of what I'm trying to say.