Quiz Entry - updated: 2026.07.14
What are the two kinds of reason/rationality, and what kind of question does each one tackle?
Theoretical reason asks what is true (beliefs and their grounds); practical reason asks what is worth doing (actions and their value).
There are two kinds of rationality:
| Theoretical reason | Practical reason | |
|---|---|---|
| Concerns | Empirical, metaphysical, logical facts and their explanation | Value questions; the desirability of actions |
| Central object | Truth of claims/beliefs and the grounds supporting them | Worth of acting; reasons that make an action worth doing |
| Lets you recognise | What counts as a good argument about knowledge | Which course of action is most desirable for reaching a goal |
A key sub-idea on the practical side is instrumental rationality: working out which action actually leads to achieving a goal or satisfying a desire.
Tip: Theoretical = "what should I believe?"; practical = "what should I do?". Same machinery (reasoning over reasons), different question.