In science, a theory is a mathematical or logical explanation, or a testable model of the manner of interaction of a set of natural phenomena, capable of predicting future occurrences or observations of the same kind, and capable of being tested through experiment or otherwise falsified through empirical observation. It follows from this that for scientists “theory” and “fact” do not necessarily stand in opposition. For example, it is a fact that an apple dropped on earth has been observed to fall towards the center of the planet, and the theories commonly used to describe and explain this behavior are Newton’s theory of universal gravitation (see also gravitation), and the theory of general relativity. In common usage, the word theory is often used to signify a conjecture, an opinion, or a speculation. In this usage, a theory is not necessarily based on facts; in other words, it is not required to be consistent with true descriptions of reality. This usage of theory leads to the common incorrect statements. True descriptions of reality are more reflectively understood as statements which would be true independently of what people think about them.


As the term is used in mainstream cognitive science and philosophy of mind, a concept or conception is an abstract idea or a mental symbol, typically associated with a corresponding representation in a language or symbology.

A vast array of accounts attempt to explain the nature of concepts. According to classical accounts, a concept denotes all of the entities, phenomena, and/or relations in a given category or class by using definitions. Concepts are abstract in that they omit the differences of the things in their extension, treating the members of the extension as if they were identical. Classical concepts are universal in that they apply equally to every thing in their extension. Concepts are also the basic elements of propositions, much the same way a word is the basic semantic element of a sentence. Unlike perceptions, which are particular images of individual objects, concepts cannot be visualized. Because they are not themselves individual perceptions, concepts are discursive and result from reason.


A framework is a basic conceptual structure used to solve or address complex issues. This very broad definition has allowed the term to be used as a buzzword, especially in a software context.

A conceptual framework is used in research to outline possible courses of action or to present a preferred approach to an idea or thought.


A model is a pattern, plan, representation (especially in miniature), or description designed to show the main object or workings of an object, system, or concept.


In logic, an argument is a set of one or more declarative sentences known as the premises (singular is also spelt “premiss” in British English), along with another declarative sentence known as the conclusion. A deductive argument asserts that the truth of the conclusion is a logical consequence of the premises; an inductive argument asserts that the truth of the conclusion is supported by the premises.

Formal and informal arguments

Informal arguments are studied in informal logic, are presented in ordinary language and are intended for everyday discourse. Formal arguments are studied in formal logic (historically called symbolic logic, more commonly referred to as mathematical logic today) are expressed in a formal language. Informal logic may be said to emphasize the study of argumentation, whereas formal logic emphasizes implication and inference.

Deductive arguments

A deductive argument is one in which it is intended that the conclusion necessarily follows from the premise. It is more commonly understood as the type of reasoning that proceeds from general principles or premises to derive particular information.


Arguments may be either valid or invalid. The validity of an argument depends on whether or not the argument follows valid logical forms, not on the truth or falsity of its premises and conclusions. The validity of an argument is not a guarantee of the truth of its conclusion, a valid argument may have false premises rendering the argument unsound. Only a valid argument with true premises has a true conclusion.


A sound argument is a valid argument with true premises.

Inductive arguments

Inductive logic is the process of reasoning in which the premises of an argument are believed to support the conclusion but do not entail it. Induction is a form of reasoning that makes generalizations based on individual instances.

 Cogent arguments

An argument is cogent if and only if the truth of the argument’s premises would render the truth of the conclusion probable (i.e., the argument is strong), and the argument’s premises are, in fact, true. Cogency can be considered inductive logic‘s analogue to deductive logic‘s “soundness.”