Premise

A premise is a proposition offered to support a conclusion. Premises are true or false statements that act as the starting points of arguments by presenting reasons to substantiate or refute assertions. Each argument is made up of a set of premises together with a conclusion. For example, the premises "all men are mortal" and "Socrates is a man" guarantee the conclusion "Socrates is mortal". In ordinary language, premises can appear in the middle of a passage, often marked by indicator words, such as since and because. In formal logic, a common approach is to write each premise on a separate line, known as standard form. Different types of premises are distinguished by their form of expression, their role in arguments, and their content. Explicit premises are overtly stated, whereas implicit premises are tacitly assumed without appearing in the text, often involving uncontroversial common-sense information shared by speaker and audience. Independent premises present distinct reasons, providing separate support for the conclusion. They contrast with dependent premises, which only work in combination. Other distinctions concern whether premises appear as first or intermediate steps in arguments, whether they are affirmative or negative, whether they refer to specific entities or make general claims, whether they are descriptive or normative, and what internal structure they have. The role of premises in arguments is typically either to preserve truth when drawing a conclusion, or to transfer justification from accepted statements to the claim for which one is arguing. To succeed, premises must be true or justified and must be relevant to the conclusion. The premises of deductively valid arguments provide the strongest support: if the premises are true, then the conclusion cannot be false. The premises of non-deductive arguments aim to make the conclusion more reasonable or increase its probability, such as inductive, abductive, and analogical arguments. Defective arguments, called fallacies, can often arise from faulty premises. For example, premises may contain false information, confuse the audience with irrelevant details, or use ambiguous terms that mislead by shifting meaning. Premises are central to many fields, including logic, argumentation theory, mathematics, philosophy, science, and law.

Definition

Premises are propositions offered to support a conclusion. They are assumptions or commitments that serve as the starting points of logical reasoning by presenting considerations to justify or refute standpoints. Each argument is made up of a set of premises together with a conclusion. For example, the argument "All men are mortal. Socrates is a man. Therefore, Socrates is mortal" has two premises ("All men are mortal" and "Socrates is a man") followed by a conclusion ("Therefore, Socrates is mortal"). As a proposition or statement, each premise is either true or false, in contrast to other types of sentences, such as questions and commands. While all premises are propositions, not all propositions function as premises: some serve as conclusions or occur outside arguments. For example, passages that simply report observations, illustrate ideas, or explain events can include statements that do not serve as premises. Premises are further distinguished from theses, which are statements someone aims to justify. Theses are similar to hypotheses, which are tentative assumptions in scientific practice that guide research and are tested by experiments. By contrast, a statement has to be offered as a reason for a conclusion to count as a premise. The strength of an argument depends on how well the premises support the conclusion. True premises can support a conclusion if they are relevant to it, whereas false premises offer no support. The word premise comes from the Latin term praemittere, meaning 'to set in front', which has its roots in the preposition prae ('pre, before') and the verb mittere ('to send'). It gave rise to the Latin term praemissa ('premise, the proposition put before'), which was borrowed into Old French as the word premisse in the 14th century. The Old French term entered Middle English with the earliest evidence of use in the late 14th century. Outside its main meaning in discourse, logic, and science, the term premises refers to a piece of land and the buildings on it. Another meaning is found in narrative theory, where the premise of a plot is the foundational idea around which the story revolves.

Identification of premises The ability to identify premises is central to understanding and assessing arguments. In ordinary language used in everyday discourse, arguments often lack a consistent or standard formal structure: the conclusion may appear before, between, or after the premises, without a fixed order to indicate whether a statement is a premise or a conclusion. This can obscure logical relationships between statements and lead to misinterpretation, particularly in complex arguments involving intertwined premises and nested sub-arguments. One way to identify premises is to look for premise indicators—verbal cues that signal where a premise begins, such as since, because, given that, and as implied by. For example, the argument "she is not at home since she has gone to the shop" begins with a conclusion and uses the term since to mark where the premise starts. However, indicator words are not always present, and even when they are, their context-dependent meaning does not guarantee that the statements they introduce are premises. To analyze and evaluate ordinary-language arguments, logicians usually try to paraphrase them in the standard form to disambiguate their components and clarify their logical structure without reyling on context-dependent premise indicators. The standard form presents each premise on a separate line, with the conclusion on the last line. A horizontal bar is often placed between the premises and the conclusion, as in:

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