is the "experiment" as founded by Galileo Galilei. We recognize an experiment by three requirements: reproducability, quantification and analysis. The third requirement, analysis, requests, that experimental results must refer to phenomena which are simple enough to be elements for theoretical descriptions. In other words, the Aristotelian physics, which referred to the motion of bodies within the atmosphere, was too complicated to give a quantitative description. The success of Galileo Galilei was the analysis of such a motion into the two elements: motion in the vacuum plus disturbance of this motion by atmospheric resistence. Only this analysis led to simple enough laws for the motion under the influence of gravity. It is what we may call "atomistic thinking", which is the result of analysis. This applies not only to the elements of matter (the true atoms and their constituent particles), but to all fields of science. The third root of the scientific method was formulated in the second half of the 17th century and I will call it "scientific reasoning". It states, that only causal reasoning (as opposed to final reasoning) is adequate for the scientific method. In other words each effect is based on a cause and we have the relation of cause and effect as the third root of our thinking. We should recall, that the two contemporates (who also exchanged letters), Kepler and Galilei, can be associated with final and causal thinking. Though Kepler had the correct laws for planetary motion, Galilei is considered the father of scientific