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"Hume showed convincingly that, if nature is uniform, inductive reasoning will work very well, whereas, if nature is not uniform, inductive reasoning will fail. This much is pretty easy to see. [Some philosophers have] suggested, however, that we should consider other options besides the use of induction for purposes of trying to predict the future. Suppose we try consulting a crystal gaze to get our predictions. We cannot say [in advance] that we will get correct predictions, even if nature turns out to be uniform, but we cannot say [in advance] that we won’t. We just don’t know... What if nature is not uniform and we do not use induction? One possibility is simply not to make any predictions at all; whether nature is uniform or not, that obviously does not result in successful predictions. Another possibility is that we adopt a noninductive method such as crystal gazing. Any method – including wild guessing – may yield a true prediction once in a while by chance, whether nature is uniform or not. But suppose that crystal gazing were to work consistently. Then, that would be an important uniformity, and it could be established inductively – that is, on the basis of the observed record of the crystal gazer in making successful predictions we could infer inductively that crystal gazing will be successful in making correct predictions in the future. Thus, if crystal gazing can produce consistent successful predictions so can the use of induction. What has just been said about crystal gazing obviously applies to any noninductive method. [Some philosophers have] therefore concluded that if any method will succeed consistently, then induction will succeed consistently. The same conclusion can be reformulated (by contraposition) as follows: If induction does not work, then no other method will work. We therefore have everything to gain and nothing to lose – so far as predicting the future is concerned – by adopting the inductive method. No other method can make an analogous claim."

I really don't seem to understand the crystal gaze example. Can someone please help me? I know I should elaborate and try to explain what I think I understood but my thoughts are too confused for that and I would need some guidance.

  • It is a "typical" philosophical argument, based on some sort of "mental experiment" trying to prove something thta is quite impossible to prove. Uniformity of nature is an assumption probbaly built-in into our (animal) harware and software. Thus, inductive reasoning very often succeed. If we can test "crystal gazing" foundi g a good percentage od predictive success, this can be perfectly compatible with non-uniformity of nature: crystal gaze can predict the result of soccer plays: this does not implies that we can use induction to predict them. – Mauro ALLEGRANZA Mar 23 '18 at 9:24
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The argument is not very well explained so it's not your fault you don't understand it.

The argument runs as follows.

Suppose that some procedure like looking in a crystal ball gives accurate predictions about the future. so every time you look in the crystal ball you get accurate predictions. They then say you can use induction to conclude the crystal ball will always be accurate. So any non-inductive method of predicting the future, like crystal ball gazing, can only work if induction works.

One reason to be confused about this argument is that it doesn't actually work. Their argument assumes that there is a method called induction that can be used to predict the future given suitable information about the past. But a set of observations implies nothing about the future except in conjunction with some law of nature, i.e. - a claim about what is happening in reality to produce those outcomes. The uniformity of nature is totally irrelevant to this problem since it doesn't specify in what respects nature is uniform. Since induction is supposed to be used to arrive at the law of nature in the first place it can't get off the ground. The reality is that there is no method that is guaranteed to give accurate predictions, or probably give accurate predictions or anything like that. The only way to find laws of nature is to guess and then criticise the guesses. This was explained at length by Karl Popper over the course of several books, see the following list for a guide:

http://fallibleideas.com/books#popper

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    "there is no method that is guaranteed to give accurate predictions": totally wrong. We can predict the movement of planets with a very very good accuracy, we can land on the Moon with a very very good accuracy, and so on. Science "works" and scientific predictions are highly reliable. – Mauro ALLEGRANZA Mar 23 '18 at 10:55
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    Those predictions are given by a physical theory not by a method. Nor is there any guarantee that those theories will continue to be accurate. Science works but it isn't guaranteed to work. The idea that theories can be guaranteed to work will discourage criticisms need to produce better theories and is therefore anti-rational and anti-scientific. – alanf Mar 23 '18 at 11:06

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