This may sound wrong, but “who said that” is a Bayesian evidence, sometimes rather strong one. If your experience tells you that given person is right in 95% of things they say, it is rational to give 95% prior probability to other things they say.
It is said that we should judge the ideas by the ideas alone. In Bayes-speak it means that if you update correctly, enough evidence can fix a wrong prior (how much evidence is needed depends on how wrong the prior was). But gathering evidence is costly, and we cannot spend too high cost for every idea around us. Why use a worse prior, if a better one is available?
Back to human-speak: if person A is a notorious liar (or a mindkilled person that repeats someone else’s lies), person B is careless about their beliefs, and person C examines every idea carefully before telling it to others, then it is rational to react differently to ideas spoken by these three people. The word “everything” is too strong, but saying “if a person C said that, I believe it” is OK (assuming that if there is enough counter-evidence, the person will update: both on the idea and on credibility of C).
Disagreeing with everything one says would be trying to reverse stupidity. There are people who do “worse than random”, so doing an opposite of what they said could be a good heuristic; but even for most of them assigning 95% probability that they are wrong would be too much.
You are right, but there is probably some misunderstanding. That the personal considerations should be ignored when assessing probability of an idea, and that one shouldn’t express collective agreement with ideas based on their author, are different suggestions. You argue against the former while I was stating the latter.
It’s important to take into account the context. When an idea X is being questioned, saying “I agree with X, because a very trustworthy person Y agrees with X” is fine with me, although it isn’t the best sort of argument one could provide. Starting the discussion “I agree with X1, X2, X3, … Xn”, on the other hand, makes any reasonable debate almost impossible, since it is not practical to argue n distinct ideas at once.
This may sound wrong, but “who said that” is a Bayesian evidence, sometimes rather strong one. If your experience tells you that given person is right in 95% of things they say, it is rational to give 95% prior probability to other things they say.
It is said that we should judge the ideas by the ideas alone. In Bayes-speak it means that if you update correctly, enough evidence can fix a wrong prior (how much evidence is needed depends on how wrong the prior was). But gathering evidence is costly, and we cannot spend too high cost for every idea around us. Why use a worse prior, if a better one is available?
Back to human-speak: if person A is a notorious liar (or a mindkilled person that repeats someone else’s lies), person B is careless about their beliefs, and person C examines every idea carefully before telling it to others, then it is rational to react differently to ideas spoken by these three people. The word “everything” is too strong, but saying “if a person C said that, I believe it” is OK (assuming that if there is enough counter-evidence, the person will update: both on the idea and on credibility of C).
Disagreeing with everything one says would be trying to reverse stupidity. There are people who do “worse than random”, so doing an opposite of what they said could be a good heuristic; but even for most of them assigning 95% probability that they are wrong would be too much.
You are right, but there is probably some misunderstanding. That the personal considerations should be ignored when assessing probability of an idea, and that one shouldn’t express collective agreement with ideas based on their author, are different suggestions. You argue against the former while I was stating the latter.
It’s important to take into account the context. When an idea X is being questioned, saying “I agree with X, because a very trustworthy person Y agrees with X” is fine with me, although it isn’t the best sort of argument one could provide. Starting the discussion “I agree with X1, X2, X3, … Xn”, on the other hand, makes any reasonable debate almost impossible, since it is not practical to argue n distinct ideas at once.