Rationality

If humans are not born with "reason" and the rational faculty develops over time and therefore through experience, isn't "a priori" essentially an impossible concept, as the rational faculty itself is developed "a posteriori"?

Comments

Exactly how 'a priori' should be defined is a delicate matter. Maybe if a newborn were put in a sensory deprivation tank it would never develop the ability to think at all, because the relevant parts of the human brain only develop properly with the help of a reasonably normal course of experience. Would that mean that there is no a priori knowledge? It seems like there might still be an interesting sense in which sentences like 'All bachelors are unmarried' or '2+3=5' are a priori.

One proposal is that we distinguish what experience it takes to understand what a sentence means from what it takes to know that it is true. We can then define 'a priori' so that however much experience it takes to understand what a sentence means doesn't count. The question becomes this. Once you understand what a sentence means, do you need additional special experience to know whether it is true? If not, then that sentence can be known a priori.

One might try a similar move in answer to your question. However much experience is required in order to develop your 'rational faculty', the question becomes whether, after that point, you need additional special experience to know the sentence in question to be true. If not, then that sentence can be known a priori.

Also, take a look at Question 1161.

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