Describing a Riemann integral using only first-order logic (FOL) poses significant challenges, as it typically requires quantifiers that extend beyond FOL's capabilities. The discussion highlights that any attempt to define integration necessitates qualifiers like "for all subsets," which FOL cannot express. The original poster struggles to formulate a definition without using existential quantifiers or infinite disjunctions, which are not permissible in standard FOL. There is an openness to being proven wrong about the limitations of FOL in this context. Overall, the consensus leans towards the belief that first-order logic is insufficient for a complete description of Riemann integration.