Mathesis Universalis, Computability and Proof

In a fragment entitledElementa Nova Matheseos Universalis(1683?) Leibniz writes "themathesis[?]shall deliver the method through which things that are conceivable can be exactly determined"; in another fragment he takes themathesisto be "the science of all things that are conceivable." Leibniz considers all mathematical disciplines as branches of themathesisand conceives themathesisas a general science of forms applicable not only to magnitudes but to every object that exists in our imagination, i.e. that is possible at least in principle. As a general science of forms themathesisinvestigates possible relations between "arbitrary objects" ("objets quelconques"). It is an abstract theory of combinations and relations among objects whatsoever. In 1810 the mathematician and philosopher Bernard Bolzano published a booklet entitledContributions to a Better-Grounded Presentation of Mathematics.There is, according to him, acertain objective connectionamong the truths that are germane to a certain homogeneous field of objects: some truths are the "reasons" ("Gründe") of others, and the latter are "consequences" ("Folgen") of the former. The reason-consequence relation seems to be the counterpart of causality at the level of a relation between true propositions. Arigorous proofis characterized in this context as a proof that shows the reason of the proposition that is to be proven. Requirements imposed on rigorous proofs seem to anticipate normalization results in current proof theory. The contributors ofMathesis Universalis, Computability and Proof,leading experts in the fields of computer science, mathematics, logic and philosophy, show the evolution of these and related ideas exploring topics in proof theory, computability theory, intuitionisticlogic, constructivism and reverse mathematics, delving deeply into a contextual examination of the relationship between mathematical rigor and demands for simplification.