Rationalism: reason, knowledge, and the philosophical tradition

Rationalism as an early modern current

Even in the earliest reference to the term, from 1539, the rationalist is one "who attaches greater importance to pure thought than to experience" for knowledge. Early modern rationalism holds that the mind can know the objective structure of reality, in the physical, metaphysical, and moral realms, and that in doing so it draws on knowledge prior to any sense experience (knowledge a priori). In his forms of argumentation he follows the methods of proof of classical geometry (more geometrico). Early modern rationalism thereby continues various scholastic positions. Historically, rationalism is usually considered to have begun with René Descartes, and Gottfried Wilhelm Leibniz and his followers (Georg Friedrich Meier, Alexander Gottlieb Baumgarten, Christian Wolff, and others) as its main representatives.

A contemporary counter-concept was "empiricism", by which is meant the view that all knowledge is based primarily on sensory perception and that there is no knowledge a priori (tabula rasa). The subsequent confrontation of rationalism and empiricism, however, dates only from the end of the 18th century. Representatives of both positions had in common that they considered revelation as a source of world knowledge superfluous or rejected it. The contrast between rationalism and empiricism is classically described as follows: A rationalist bases his philosophical explanation of the world primarily on deductive reasoning, while an empiricist accepts only hypotheses that can be confirmed inductively by traceable observations. However, it is not a blanket statement that authors described as rationalists would generally reject sensory experience as a source of knowledge - and empiricists would reject reason. In fact, empiricist elements can always be found in the texts of rationalist philosophers, and vice versa.

Rationalism in Philosophy of Religion and Theology

In the context of philosophy of religion and theology, "rationalism" refers to positions that credit human reason with knowledge of the divine and that hold that philosophical theology, without the presupposition of revelation or grace, is permissible and feasible. An alternative name for these positions is also "intellectualism." Such a position is closely associated with certain theological content that can be considered a consequence or a presupposition of rational access, e.g., that divine will and action follow logical and metaphysical rules and occur for reasons. This is usually accompanied by the assumption of stable and recognizable ontological structures and moral principles and criteria to which the divine will conforms or which correspond to it, which can lead to God being identified by some representatives with a kind of supreme reason. The counter-positions, on the other hand, argue that the divine will and action are completely arbitrary (voluntarism), or that the individual moments of time are each momentarily caused by God and only seem to represent a sequence of events (occassionalism). Both counter-positions want to achieve that the divine will is not bound to any logical or other principles and thus must remain rationally incomprehensible. Such controversies are debated in Islamic theology as well as in Christian scholasticism and the rational theology of the Enlightenment epoch.

In a somewhat different and rather rare usage, "rationalism" in theology or the history of theology can also mean that e.g. aspects of the personhood of the divine that (actually or supposedly) cannot be reconciled with strong claims of rationalizability are considered dispensable. Conversely, one then speaks e.g. of "voluntarism" when the divine is certainly described or conceived as a person with will, exercise of actions etc..

16th-17th century

In many respects, rationalism draws on the terminology and method of Latin scholasticism, but it claims to be an independent new approach. This was preceded by a spreading resentment, especially in early seventeenth-century France, of alleged "barren sophistry" of scholastic debates; this resentment can also be traced to a general desire to end confessional conflicts. The theological debates, contested on metaphysical grounds, would, according to a common charge at the time, merely pave the way for moral skepticism. In contrast, rationalism sought to argue in a methodologically rigorous manner and to dispense with the interpretation of authority in its reasoning. In the process, there was a shift of thematic attention from the religious doctrine of salvation to the technical mastery of nature, as Francis Bacon had proposed.

Epistemological rationalism was also applied in other areas of philosophy, such as ethics and the philosophy of law. Thus, the opinion was held that the elementary principles of human morality and natural law resulted from pure reason (see Samuel von Pufendorf, Thomas Hobbes, Baruch de Spinoza, in a broader sense also Immanuel Kant, G. W. F. Hegel and others). In the philosophy of religion, deism first followed rationalist approaches when it postulated fundamental religious principles that were knowable. This makes historical revelation seem superfluous and led to theological rationalism.

René Descartes is considered to be the founder of classical rationalism (also known as "intellectualism"), receiving important inspiration from Marin Mersenne. Descartes began a reformation of science and philosophy along the lines of geometry. He used the axiomatic structure of Euclid's Elements as a model. According to this, universal principles can be deduced from basic concepts with the help of the intellect. All other questions of philosophy and natural sciences can be answered by deduction of theorems from these principles and their application to specific problems (corollaries). Descartes claimed that such principles could not be inferred by means of sense perception. Sense perception was regarded as a source of perception distinct from the mind, but one that produces only fuzzy and uncertain knowledge that has no standing before Descartes' methodological doubt. The origin of these basic concepts, or the question of what belonged to their scope, was an open question of the rationalist research program.

In this phase, rationalism was opposed by moral sceptics such as Pierre Bayle or apologists such as Blaise Pascal, who denied the ability of reason to arrive at universally valid and unquestionable propositions about morality or the relationship between soul, world and God.

18th century

Nicolas Malebranche in France, the Dutch philosopher Baruch Spinoza and the German polymath Gottfried Wilhelm Leibniz and others further developed Cartesian rationalism and established its position as the main philosophical current at the continental European universities of the 18th century. In the process, they came into conflict not only with orthodox positions of all Christian denominations, but also with followers of the materialist Pierre Gassendi, the empiricist John Locke, or, for example, the disciples of Isaac Newton, even if in part only as a result of coincidences in the history of science (e.g., the Priority Controversy).

Empiricism challenged the basic concepts of the rationalists precisely because they were not supposed to derive from sense perception. According to the empiricist, however, only that which has been derived from observations and is confirmed by them can - roughly speaking - be recognized as knowledge. The epistemological scepticism of David Hume equally takes up the criticisms that both currents raise against each other: empiricist induction cannot lead to strictly generally valid propositions; rationalist deduction rests on uncertain premises. Rationalism finally finds its way to a system of encyclopedic completeness in Christian Wolff.

Immanuel Kant, also a mastermind of the Enlightenment, explicitly understood his transcendental philosophy as a mediation of rationalism and empiricism. The deductive-rationalist structure is accepted, with various reservations, even if there is no basis for basic concepts from perceptions of the senses, but only if these concepts derive from an analysis of transcendental structures of reason and perception itself, i.e. from a critique of pure reason. The basic structures of the cognizable world can thus be enunciated in principles that emerge as synthetic judgments a priori from the conjunction of the forms of sensibility and reason. For Kant, sensibility and reason are not separate strands of cognition, but together the "stems" of experience fitting into rational rules.

19th century - present

Rationalist positions are currently part of various epistemologies, in the predominantly German discourse theories, in economic theories such as game theory and rational decision theory, and in predominantly Anglo-American theories of international relations. However, these are not always rationalist positions in the narrower sense (see above), but they have in common that they presuppose rationality in thought and action. The difference between rationalism and theories of rationality is, however, often only blurredly seen even by the opponents of these positions. This can be seen with regard to irrationalism, which has been built up as an opposing concept since the middle of the 19th century (in Romanticism).

Within the framework of cultural criticism, a broad critique of rationalism developed, among others in Oswald Spengler and Martin Heidegger, and later in numerous philosophers of the French Nietzsche reception and post-structuralism with quite different thrusts. Against these positions and in relation to further philosophical developments, rationalist new approaches have turned in various systematic areas, for example in modern representatives of Theological Rationalism or Critical Rationalism in the field of philosophy of science.

This often leads to critical differentiations of the concept of rationality. Particularly influential is "communicative rationality", as coined by Jürgen Habermas and developed together with Karl-Otto Apel and many other philosophers. Julian Nida-Rümelin prominently advocates a "structural rationality" in the German-speaking world, on which his "rational ethics" is also based. In the work of Herbert Schnädelbach, three basic types of rationality are named; the debate initiated by him now distinguishes around fifty different types of rationality.