THE SOCIAL CHARACTER OF RATIONALITY
Davidson, ‘Rational Animals’
1. Rationality requires having propositional attitudes.
2. Determining whether a being is rational cannot be done without determining
whether that being has propositional attitudes.
An argument from semantic opacity
3. The contents of propositional attitudes are semantically opaque. For example, if a
being believes that Superman can fly, it does not follow that she believes that
Clark Kent can fly.
4. It is possible to determine whether the contents are opaque only if that being has a
language.
5. So, if 3 and 4, one can determine whether a being has propositional attitudes only
if that being has a language.
6. So, only language using creatures can be deemed rational.
An argument from the holism and observability of propositional attitudes
7. Propositional attitudes are holistic: if a being has one propositional attitude, such
as a belief, she has many; and if a being has beliefs, then she also has desires and
intentions.
8. Propositional attitudes are observable: if a being has a propositional attitude, such
as belief, then an interpreter can deduce from the being’s behaviour that the being
has that propositional attitude.
9. So, if 6 and 7, in order for a being to have a single thought, that being must
engage in a complex pattern of behaviour.
10. Such complex patterns of behaviour require language.
11. So, if 8 and 9, only language-using creatures have propositional attitudes.
12. So, only language-using creatures are rational.
An argument from the requirements of belief
13. Belief is the most basic sort of propositional attitude.
14. To have one belief requires a background of beliefs.
15. To have a belief requires the concept of belief.
16. To have the concept of belief requires the concept of intersubjective truth.
17. To have the concept of intersubjective truth requires linguistic communication.
18. So, having the concept of belief requires having a language.
19. So, only language-using creatures have beliefs.
20. So, only language-using creatures have propositional attitudes.
21. So, only language-using creatures are rational.