Betting and Presuming: From God’s Existence to Morality and Law

Pascal famously argued that since God transcends the rational domain of demonstration, we must bet on his existence. Less famously, Leibniz claimed that in the absence of a full-fledged demonstration of God’s existence, we at least have to presume, that is to say, to assume, that he exists until the contrary is proved. Aside from marking a significant contrast between these two leading figures of modern philosophy (Leibniz would later reproach Pascal for having “paid attention only to moral arguments”), these two stances are at the origin of two independent developments: decision theory and presumptive reasoning, respectively. In this paper we will provide a critical account of Pascal’s and Leibniz’s lines of thought by first presenting the original arguments and then reconstructing them in light of the developments they gave rise to. Finally, we will advance some remarks about the interplay of presumption and probability in Leibniz’s approach to morality and law.