Speculative reason, sometimes called theoretical reason or pure reason, is theoretical (or logical,

deductive Deductive reasoning is the mental process of drawing deductive inferences. An inference is deductively valid if its conclusion follows logically from its premises, i.e. if it is impossible for the premises to be true and the conclusion to be false ...

) thought, as opposed to practical (active, willing) thought. The distinction between the two goes at least as far back as the

ancient Greek philosophers Ancient Greek philosophy arose in the 6th century BC, marking the end of the Greek Dark Ages. Greek philosophy continued throughout the Hellenistic period and the period in which Greece and most Greek-inhabited lands were part of the Roman Empire ...

, such as Plato and Aristotle, who distinguished between theory (''theoria,'' or a wide, bird's eye view of a topic, or clear vision of its structure) and practice (''praxis''), as well as '' techne''. Speculative reason is contemplative, detached, and certain, whereas practical reason is engaged, involved, active, and dependent upon the specifics of the situation. Speculative reason provides the universal, necessary principles of logic, such as the principle of

non-contradiction In logic, the law of non-contradiction (LNC) (also known as the law of contradiction, principle of non-contradiction (PNC), or the principle of contradiction) states that contradictory propositions cannot both be true in the same sense at the sa ...

, which must apply everywhere, regardless of the specifics of the situation. On the other hand, practical reason is the use of reason to decide how to act. It contrasts with theoretical reason or speculative reason. Some may try and refer to practical reasoning as moral reason but this kind of reasoning actually falls in line more so with theoretical reasoning as it's a contrast of practical reason. This has little to do with what's practical as practicality involves specific action, decision, and particulars which all have a logical undertone without bias toward an ideology. Moral reason finds itself being more malleable in its spectrum of reasoning and had the possibility of being skewed by faith and belief. This will lead to discrepancies in practicality given the nature of morals being a culture specific outlook, and will reduce the practicality in an outcome as each individual has a separate point of view and can change the outcome of moral reasoning. Yet there are philosophers who have erected systems based on this distinction. Two philosophers who have done so are

Thomas Aquinas Thomas Aquinas, OP (; it, Tommaso d'Aquino, lit=Thomas of Aquino; 1225 – 7 March 1274) was an Italian Dominican friar and priest who was an influential philosopher, theologian and jurist in the tradition of scholasticism; he is known w ...

(who follows Aristotle in many respects) and Immanuel Kant.Karim Mojtahedi, ''Kant's Critical Philosophy'', Tehran: Amir Kabir, 1999

References

{{DEFAULTSORT:Speculative Reason Reasoning Philosophy of Aristotle Concepts in epistemology Concepts in logic Critical thinking Deductive reasoning Epistemology Immanuel Kant Logic Philosophy of logic Platonism Thomas Aquinas Thought