Social Research Glossary


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Citation reference: Harvey, L., 2012-20, Social Research Glossary, Quality Research International,

This is a dynamic glossary and the author would welcome any e-mail suggestions for additions or amendments. Page updated 19 December, 2019 , © Lee Harvey 2012–2020.


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core definition

Rationalism is a theory that recognises reason as the unique source of true knowledge.

explanatory context


For rationalists, knowledge is possible through reason alone.

Rationalism was one of two approaches that dominated 17th century Western philosophy, the other being empiricism. Descartes, Spinoza and Leibnitz are regarded as the triumvirate of classical rationalists.

Rationalism is opposed to empiricism, which makes experience (sensory perception, etc.) rather than reason the source of knowledge.


Cartesian metaphysics underpins much rationalist thought. Later rationalists, such as Spinoza and Liebnitz, in their different ways, attempted to reconcile the dualism created by Descartes whilst retaining the centrality of reason (and of god).

Both these later rationalists proposed a world very different from the world of appearances.

Types of rationalism

Cartesian rationalism

Cartesian metaphysics is the name given to the rationalist perspective developed by Descartes in the first half of the 17th century. It embodies a view of science, of truth and of the relation between knowledge, knowing and a 'higher' metaphysical entity (or 'God')

Descartes saw all science as unified and interconnected.

Descartes maintained that mathematical logic was the exemplar that underpinned his new system of knowledge and that was applicable to all forms of science.

Descartes (following Bacon) claimed to have revolutionised method. His method was the 'method of doubt'. That is, (in theory) he calls into question all preconceptions. (In practice, however, he never called into question his own preconceptions about the existence of God).

The method of doubt ultimately casts doubt on all empirical observation about the external world as it may be the result of deceived senses, perhaps of dream.

However, Descartes argued that there could be no doubt about his own existence as long as he thought he was something. This is the famous cogito ergo sum or je pense, donc je suis (I think therefore I am). Descartes' revolution was, thus, essentially an idealist one. It comprises the radical separation of mind and matter and the assertion that the only tangible proof of existence is thought. Descartes takes this one stage further to argue that thought must be guaranteed by God. God therefore exists; because God exists Descartes thinks and because Descartes thinks Descartes exist; at the very least as a thinking being. This circular proof of the existence either of God or of Descartes' thought is called the ontological proof of the existence of God.

Descartes defined 'substance' as what really exists. That is, that which requires nothing but itself in order to exist. For Descartes, the only substance must be god, as supreme being, requires nothing else for its existence. In these ways, Descartes retained the idea of 'God' as central to his metaphysical system.

However what this proof does not do is guarantee the material reality either of the earth, material objects or individuals.

The Cartesian view is thus at variance with empiricism as it supposes that people can grasp general truths about reality independently of experience.

Descartes' dualist (mind-matter) approach both retains much conventional knowledge in the sense of conserving the ideas of self, god and the material world. It also provides for a differentiation between the concerns of secular science (the study of the material world) and those of religion (the study of the spiritual, or realm of the mind).

Radical unitary rationalism

Radical untitary rationalism was an attempt to develop the Cartesian view of rationalism and to confront the dualism of mind and matter that Descartes had proposed.

Spinoza, in developing rationalism, argued that the world was unitary, that the totality was in effect one substance and any apparent diffference was merely a different facet of the substance.

For Spinoza, the totality was a sort of fusion of nature and god. Nature is the totality of god's activity, it is perfect and therefore divine. Further, god could not be separate from the world because that would make god finite rather than infinite (which for Spinoza was irrational). There is, thus, no supranatural realm in Spinoza's view.

Spinoza solves the Cartesian dualist problem, in effect, by denying its possibility. Everything is part of the one unitary substance that has an infinity of attributes.

Of the infinity of attributes of the totality, Spinoza argued that only two are accessible, the rest is faith. The two accessible attributes are thought (or consciousness) and extension (which are identifiable objects). Identifiable objects are simply temporary contours on the fabric of the totality.

Spinoza, like Descartes has a circular argument of the existence of god, but he differs in asserting the unitary nature of all things.

There is not much room for a common sense notion of freewill in this radical unitary approach to rationalism. Indeed, Spinoza suggests that such a notion is illusory as we are part of god's totality. However, human's delude themselves into thinking that they are caused to act in ways which are in effect the processes of human servitude (or oppression).

Radical non-unitary rationalism

Radical non-unitary rationalism is a rather strange idea for modern readers based on the idea that the world consists only of spiritual entities.

Liebnitz argues that there is an infinity of spiritual items or souls called monads. These souls range from god through humans to the ultimate constituents of material things. It is thus mistaken to refer to matter as distinct from spirit or mind. It is all part of the same infinite realm of non-reducible elements. Anything that can be called matter can be further reduced to its simple (spiritual) elements. There is no mind-matter dualism for Liebnitz as all matter is essentially phenomenal; it is not real matter, if it exists it is mental in some form.

Liebnitz explains what appears to be causality by arguing that in the infinite array of monads each has perception of all the others and they do not interact but simply correspond. Thus there is a pre-established harmony in this mutual awareness of monads that proves the existence of god.

There is then no need for notions of causality, as it is god who is doing everything all the time. This seems to inhibit any idea of freewill, but Liebnitz gets round this by suggesting that while god creates all monads and equips them for action they are perfectly self-determinimg.

analytical review

The BBC (2009) website states:

Rationalism is an approach to life based on reason and evidence.

Rationalism encourages ethical and philosophical ideas that can be tested by experience and rejects authority that cannot be proved by experience.

Because rationalism encourages people to think for themselves, rationalists have many different and diverse ideas and continue in a tradition from the nineteenth century known as freethought.

However, most rationalists would agree that:

  • There is no evidence for any arbitrary supernatural authority e.g. God or Gods.
  • The best explanation so far for why the natural world looks the way it does is the theory of evolution first put forward by Charles Darwin.
  • All human beings should have fundamental rights. Some rationalists and humanists go further and argue that animals should also have rights as they are living, sensate beings.
  • Society is should be an "open society", where each individual is able to live "freely and equally practise their chosen life stance, and in which human potential is realised to the benefit of the individual and the community at large." (Levi Fragell, President of International Humanist and Ethical Union, 2001)

New World Encyclopedia (2014):

Rationalism is a broad family of positions in epistemology. Perhaps the best general description of rationalism is the view that there are some distinctive aspects or faculties of the mind that (1) are distinct from passive aspects of the mind such as sense-perceptions and (2) someway or other constitute a special source (perhaps only a partial source) of knowledge. These distinctive aspects are typically associated or identified with human abilities to engage in mathematics and abstract reasoning, and the knowledge they provide is often seen as of a type that could not have come from other sources. Philosophers who resist rationalism are usually grouped under the heading of empiricists, who are often allied under the claim that all human knowledge comes from experience.

associated issues


related areas

See also





BBC, 2009, Rationalism, last updated 27 October 2009, available at, accessed 8 April 2013, still available 13 June 2019.

New World Encyclopedia contributors, 2014, 'Rationalism', New World Encyclopedia, last updated 29 May 2014, available at:, accessed 21 May 2017, still available 13 June 2019.

copyright Lee Harvey 2012–2020


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