The science of reasoning is most closely associated with logic.

Here's why:

* Logic is the study of valid reasoning. It provides the rules and principles for determining whether a conclusion follows logically from a set of premises.

* Formal Logic is a branch of logic that deals with the structure and form of arguments, using symbols and formal systems.

* Informal Logic focuses on the everyday use of reasoning, analyzing arguments for their soundness and cogency.

While other fields like philosophy and cognitive psychology also study reasoning, logic is the core discipline dedicated to its systematic analysis and application.