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Science and the claim that observation is theory laden


To: Chris M.
From: Geoffrey Klempner
Subject: Science and the claim that observation is theory laden
Date: 30th March 2010 13:15

Dear Christian,

Thank you for your email of 21 March, with your essay for the University of London Logic BA module, in response to the question, 'Scientific claims cannot be objective, because their justification relies on observation, and observation is theory-laden.' Discuss.

You cover a lot of ground in your answer to this question. You look at Quine's image of a network of beliefs on which experience impinges at the edges, you mention Kuhn and incommensurable paradigms, and inferences from the familiar illusions of perception to the effect that all seeing is in some sense 'seeing as', as well as Fodor's defence of 'cognitively inpenetrable perceptual modules' (pointing in the other direction, towards a theory-neutral perceptual content), then finally at the end you throw in Grover Maxwell's idea that the observation-theory distinction is relative not absolute.

The traditional example is the Church's opposition to the use of the telescope in the early part of the 17th century. When the telescope was pointed at the Moon, it clearly revealed mountains and craters -- but only to those who accepted the theory of how telescopes work. To churchmen who 'new' that the Moon had a smooth, glassy surface all the observations proved is that the Devil was at work confounding our perceptions.

Now, anyone could look through the telescope and draw, accurately, what they saw. How is it that the churchmen didn't see what was there to be seen?

There is a point to make about the remarkable human capacity to refuse to believe what we see (because we 'know' we can't be seeing it). And it is also tempting to hook this up with Kuhn's idea of incommensurable paradigms. However, if one looks at 'real science' what happens is not that one researcher refuses to 'see' an observation made by another researcher. Rather, problems with a theory are first revealed as 'anomalies' in observations, with the defenders of the old paradigm insisting that these are not significant, while the critics of that paradigm insist that the anomalies are significant.

How do you decide questions of 'significance'? What we are talking about is not so much observations as such, as patterns of observation, or observation report, over time.

Thus, the original question, could be posed again: 'Scientific claims cannot be objective because their justification relies on recognition of the significance of patterns of observation over time, and what is or is not significant depends on a prior theory.' This looks less threatening, if only because the claim that an observed anomaly is not significant looks less and less plausible, as the anomalies increase.

However, there is another factor to take into consideration, which is that the design of experiments is heavily dependent on theory. You more or less make this point. There are always less chances of finding what you were not looking for, than there are of finding what you were looking for. The point here, however, is that it IS possible to 'not find what you were looking for'.

What this doesn't allow for, of course, is the possibility that there are two (or more!) theories which explain all the observations equally well. According to theory 1, the observations confirm theory 1, while according to theory 2, the observations confirm theory 2. In that case, there really is a problem of objectivity.

But how often does that occur in 'real' science? It is very rare that we have one theory that is fully consistent with the observations, let alone more than one. In a possible universe where there were lots of equally good incommensurable theories we would have strong grounds for doubting the objectivity of scientific claims. But the mere thought that our universe might, theoretically, be like that isn't in itself sufficient to raise doubts. The situation here can be compared with classic sceptical scenarios, where the mere fact that you can imagine some wild sceptical hypothesis isn't itself grounds for doubt.

In other words, in order to make the original statement that 'scientific claims cannot be objection because... observation is theory-laden' plausible, it is necessary to imagine possible worlds which are significantly different from the actual world. If the universe is the creation of a Cartesian-style 'evil demon' then there might be all sorts of ways in which honest investigators might be tricked into thinking that a theory had been 'confirmed' when in fact it had not. But that isn't our universe, at least, not so far as we have been able to observe (!).

These are just some thoughts which you might find helpful (or provocative). I think an examiner would be impressed by the amount of material which you have covered. If there is a criticism to make, it is that I don't have a clear picture of your all-things-considered view on this.

All the best,