Where does the uncertainty of our knowledge of natural world come from? Does our knowledge turn more reliable after our acceptance of the need of the mathematization of nature and formalization of the experiment results? Is there between the above mentioned poles (i.e. uncertainty vs. unquestionable knowledge built after the model of the mathematization of the experiment results) any other epistemic space which made the guaranteed certainty in physics possible? Should this certainty be conceived – on the background of the absolute or metaphysical certainty – as insufficient, or as an application of the mathematical model? Leibniz stands for the idea that the high probability of moral certainty could reach the truth of the latter. The aim of the paper is to analyze this very probability logic with attention paid to making use of it in natuaral philosophy.