Principle of rationality

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The 'principle of rationality' (or 'rationality principle') is coined by Karl R. Popper in his Harvard Lecture of 1963, published in his book Myth of Framework.[1] It is related with what he called the 'logic of the situation' in an Economica article of 1944/1945, published later in his book The Poverty of Historicism.[2]

Following Popper the 'logic of the situation' is the result of reconstructing meticulously all circumstances if you are trying to understand a historical event. The 'principle of rationality' is the assumption that people try to reach their goals. Both the reconstruction of the 'logic of the situation' and the application of the 'principle of rationality' constitute an important method of understanding that seems to be useful in all social sciences. It is the method of creating theories due to our knowledge that men and women usually have goals and usually try to reach their goals. If this method is applied to a particular situation it results in a theory which can be proved as right or wrong. Although the 'principle of rationality' is not applicable to (natural) science there is no methodological difference between science and social sciences because both sciences are getting explanations by inventing theories which can be proved.

Popper called his 'principle of rationality' nearly empty (a technical term meaning without empirical content) and strictly speaking false, but nonetheless tremendously useful.[3] These remarks earned him a lot of criticism because seemingly he had swerved from his famous Logic of Scientific Discovery.

Among the many philosophers having discussed his 'principle of rationality' from the 1960s up to now are Noretta Koertge, R. Nadeau, Viktor J. Vanberg, Hans Albert, E. Matzner, Ian C. Jarvie, Mark A. Notturno, John Wettersten, Ian C. Böhm.


In the context of knowledge-based systems, Newell (in 1982) proposed the following principle of rationality: "If an agent has knowledge that one of its actions will lead to one of its goals, then the agent will select that action."[4] This principle is employed by agents at the knowledge level to move closer to a desired goal. An important philosophical difference between Newell and Popper is that Newell argued that the knowledge level is real in the sense that it exists in nature and is not made up. This allowed Newell to treat the rationality principle as a way of understanding nature and avoid the problems Popper ran into by treating knowledge as non physical and therefore non empirical.

See also[edit]


  1. ^ Karl R. Popper, The Myth of Framework, London (Routledge) 1994, chap. 8.
  2. ^ Karl R. Popper, The Poverty of Historicism, London (Routledge) 1960, chap. iv, sect. 31.
  3. ^ Karl R. Popper, The Myth of Framework, London (Routledge) 1994, chap. 8, sect. 12.
  4. ^ Allen Newell. The knowledge level. Artificial Intelligence, 18:87-127, 1982.