A justification: "we know A is true because B is true."
A mental causation: "I concluded A because first I believed B and that led me to A."
There is certainly a strong relationship between justifications, and stories of mental causation.
They are not the same. A person may think A as a result of thinking B, even though it is not valid or reasonable to do so.
We may think of a justification as a story of mental causation that we approve of. If we agree that a person who thinks B should conclude A, then we would say that B is a valid justification for A. We would say, equivalently, they are justified in concluding A. To say an inference is justified is to say we approve of it.
This is the case even if the inference is not formally valid. A witness in a trial says, "I saw the criminal's face and he looked just like the defendant, so I conclude they are the same person." That's not a formally valid deduction - there are all sorts of ways two people could look the same without being the same. But we might consider it a reasonable justification. And by this we mean that we approve of it.
We may say that a particular way of allowing one thought to cause another is a "method of thought." What does this approval of methods of thought entail? Not necessarily an exhaustive list, but:
- We approve of methods of thought that, when the same rules are applied to practical pursuits, result in the achievement of practical goals. A carpenter uses trigonometry to measure wood to help build a house, giving a practical, useful result. So, we approve of the trigonometry and of the methods of mathematical thought that support it.
- We approve of methods of thought that we already use
- We approve of methods of thought used by those we recognize as experts in a domain
- We approve of methods of thought that do not lead themselves to contradictions.
- We approve of methods of thought that can produce full explanations of their subject matter
- We approve of methods of thought that are simpler to remember and work with, a la Occam's razor
Where - besides C.S. Peirce - can I see this relationship between justification, and mental causation, discussed?