The Contingency Argument (Leibniz)

Gottfried Leibniz articulated the Principle of Sufficient Reason: every fact or true proposition has an explanation for why it is the case. Applying this to existence, Leibniz argued that the sum of all contingent beings — beings that could have been otherwise or not existed at all — requires an explanation beyond itself. That explanation cannot be another contingent being without regress. It must be something whose explanation is contained in its own nature, what philosophers call a necessary being.\n\nThe argument does not depend on any empirical claim about the universe's age or origin. It turns on the metaphysical relationship between contingent and necessary. If any contingent thing exists, and every contingent thing requires a reason, then a non-contingent ground must exist. Classical theism identifies this ground with God.\n\nContemporary defenders include Alexander Pruss and Joshua Rasmussen. Critics, such as David Hume and Bertrand Russell, have denied the Principle of Sufficient Reason itself, or have proposed that the universe as a whole may be a brute fact needing no explanation. The argument's force therefore depends on whether one accepts PSR — but if one does, the conclusion follows with considerable rigor.