For the most part I agree with what you say, but there was one passage with
which I do not. At one point you say:
>In particular, it is noted that since all observation is theory-laden, it
>not actually possible to falsify anything with 100% certainty. You can
>never be sure if the failure of your observation is due to a failure of
>the hypothesis under test or to failure of some assumption which was made
>when making the observation.
In point of fact you can often be sure. I think I understand what you mean
by "theory-laden". Scientists will use theories to determine what
observations/experiments should be done. But far more often than not the
observations give results that directly contradict the theory. This is
usually not due to a badly designed observation, but to a badly designed
theory. I agree that 100% certainty is not possible, but show me a human
endeavor where it is possible.
Let my try to illustrate this with a couple of examples.
Example 1: Hypothesis -- Drug X does not inhibit the activity of enzyme E.
Experiment -- Take two flasks each containing an equal volume of a solution
of E; make sure that both volumes have the same concentration of enzyme. To
one flask add X; to the other flask add an equal volume of water to make
sure the concentrations in both flasks remain the same. Incubate both
flasks in the same 37 degree waterbath for one hour. Then remove
equal-volume aliquotes from both flasks and test the activity of E. If the
results are the same for both flasks, then the hypothesis has been verified.
If, however, the activity of the flask that contained X is significantly
lower than that of the flask that had water added to it, then the hypothesis
has been refuted. And 100% certainty is not needed, because the
experimental design eliminates having to make "assumptions" about what is
Example 2: Hypothesis -- Drug X kills cancer cells, but has no affect on
normal cells. Experiment -- Take a batch of cells and split them in half.
Transform one group so that it becomes cancerous. Split the cancerous group
into two more groups, one of which will get X, the other straight media.
Split the normal group into two groups as well, one of which will get X, the
other straight media. Count the number of cells in each group. Incubate
the cells for 72 hours in a tissue culture incubator, then count them again.
The normal-media group will provide your baseline results. The hypothesis
will be verified if there are significantly fewer cells in the cancerous-X
group (compared to the normal-media group), but there is no significant loss
of cells in either the cancerous-media group or the normal-X group. The
hypothesis will be refuted, however, if there either is no significant cell
loss in the cancerous-X group, or there is significant cell loss in the
normal-X group, or both, but there is no significant cell loss in the
cancerous-media group. Ambiguous results would include no significant cell
loss in normal-X but significant cell loss in both cancerous groups, or
significant cell loss in all groups, or significant cell loss in the
normal-media group but not in any other group. Again, the way the
experiment was set up eliminates observational "assumptions" and yields
results that can be considered as close to being 100% certain as it is
possible to get.
Kevin L. O'Brien