Refining Reid's principle of credulity

Our response to testimony changes over time

We all have a powerful, innate tendency to accept other people's testimony. We respond to testimony as if that response were governed by the defeasible acquisition rule: Accept others' assertions. This propensity, as Reid says, is unlimited in children, but as people grow up they learn to resist it.

People can respond to the same testimony in different ways

The factors that cause us to override the acquisition rule are learnt and there's no reason to think that everyone learns the same set. The fact of cognitive diversity also shows that not all people respond to testimony in the same way.

We are recipients of testimony before we are transmitters or originators of testimony

Michael Dummett has persuasively argued that learning your first language goes hand-in-hand with acquiring beliefs through testimony. Before somebody can make an assertion they have to know a language.

Perceptual knowledge presupposes testimonial knowledge

Perception needs to be distinguished from perceptual knowledge. We cannot help but perceive when we're conscious, but acquiring perceptual beliefs involves making a judgement about our surroundings and that requires knowing a language and that means being in possession of testimonial knowledge.

We cannot avoid acquiring false beliefs through testimony

Our natural response to testimony is to accept it. We have to learn to override the acquisition rule, but it's impossible to devise a foolproof set of overriding factors that prevent us from acquiring any false beliefs at all.