As we have already mentioned, the problem regarding the innermost meaning of Leibniz's thought is very difficult to solve. Over and beyond any comprehensive reconstruction of his thought, I would like to dwell on the definitions of "calculating thought" and "meditating thought," to find in Leibniz the dimension and the modes within which this polarized field is made manifest. If there is no question about the unified nature of Leibniz's thought, we may still point to some themes that are quite far removed from one another, and thus reveal the breadth of range and consequent internal multiplicity of meanings of his philosophy. The themes of the calculus, of the combinatoria, of mathesis and the characteristica universalis are all reflections of Leibniz's mathematical spirit. Starting from the years 1669–1670, Leibniz elaborated scientific projects of a logicalmathematical nature, which led him to study physical and natural phenomena in general. We can outline a precise itinerary, going from the preparatory studies for the Theoria motus abstracti (1669–70), and the Specimen Demonstrationum de Natura Rerum corporearum (1671), to the Summa Hypotheseos physicae novae (1671), and some preparatory tables for the study of the universal characteristic (1671–72), thus realizing at once the importance of mathematics for him.