

The strongest form of support is found in deductive arguments: it is impossible for their premises to be true and their conclusion to be false. An argument is correct if its premises support its conclusion. The arguments or inferences made up of these propositions can be either correct or incorrect. Logically true propositions constitute a special case since their truth depends only on the logical vocabulary used in them.

In either case, the truth of a proposition usually depends on the denotations of its constituents. Simple propositions have subpropositional parts, like singular terms and predicates. Complex propositions are made up of other propositions linked to each other by propositional connectives. Premises and conclusions are usually understood either as sentences or as propositions and are characterized by their internal structure. It studies arguments, which are made up of a set of premises together with a conclusion. Logic is based on various fundamental concepts. But it is also common to link their difference to the distinction between formal and informal fallacies.

Another characterizes informal logic as the study of ampliative inferences, in contrast to the deductive inferences studied by formal logic. One prominent approach associates their difference with the study of arguments expressed in formal or informal languages. There is no general agreement on how the two are to be distinguished. Formal logic contrasts with informal logic, which is also part of logic when understood in the widest sense. When used as a countable noun, the term "a logic" refers to a logical formal system. In this sense, it is equivalent to formal logic and constitutes a formal science investigating how conclusions follow from premises in a topic-neutral way or which propositions are true only in virtue of the logical vocabulary they contain. It is often defined in a more narrow sense as the science of deductively valid inferences or of logical truths. Logic is the study of correct reasoning or good arguments.
