"On the other hand, as I understand it, Art is referring to the phenomenon that philosophers of science since Thomas Kuhn delight in pointing out; namely, that 'all data is theory-laden' (or some similar phrasing). In other words, even the observed data depend to some extent on the presuppositions of the investigator. It is these presuppositions which (I think) Art is referring to as 'bias'."
I'm not so sure, but then I'm not so sure I am right to argue the point, at least excessively.
"Steve Clark pointed out in an earlier post that many practicing scientists are rather poor philosophers of science."
And many philosophers of science are poor scientists. Most have never set foot in a lab; those that have had been away for years by the time they began publishing as philosophers. That such people would try to dictate what the limits and influences of scientific research should be is extremely amusing. They remind me of armchair quarterbacks. It seems to me that the best judges of the limits and influences of scientific research are those who do science every day, people like you and me.
"Your posts seem to be claiming that these things simply don't influence your work in the lab. Are you sure?"
Yes. "[I]nvestigator presuppositions" do not alter the outcome of experiments; no amount of wishing, or assumption, or interpretation, can change a negative result into a positive result, or vice versa. Unambiguous data doesn't need interpretation; ambiguous data cannot be properly interpreted. Data that supports a theory cannot be interpreted to refute it; data that contradicts a theory cannot be interpreted to verify it. The only thing that is "theory-laden" is how the data is defined and described. For example, if macroevolution is defined as speciation, then observed events of speciation support the reality of macroevolution. If, however, macroevolution is defined as the appearance of novel structures, then observed events of speciation do not support the reality of macroevolution. The data is exactly the same in both cases, and it is interpreted in exactly the same way - a new species appears, but whether or not it supports the reality of macroevolution depends upon how yo
u define macroevolution, and that is "theory-laden".
But it has nothing to do with how data is interpreted.
Kevin L. O'Brien
"Good God, consider yourselves fortunate that you have John Adams to abuse, for no sane man would tolerate it!" William Daniels, _1776_