Kathy, (01)
I just wanted to make it clear that logic, by itself, cannot derive
a contradiction from any collection of positive observation statements,
no matter how absurd they may sound. (02)
> The statement "The bar has length 7.1 cm AND the bar has length
> 6.8 cm" is a contradiction. (03)
By themselves, the two statements are not contradictory, but
a contradiction arises as soon as you add an axiom about length: (04)
No object can have two different lengths at the same time. (05)
This is a principle of ontology, which introduces a negation.
In conjunction the two positive statements, the negative
statement can generate a contradiction. (06)
I agree that the following statement can be true, even in conjunction
with the above ontology: (07)
> The statement "Sensor A observed the bar to have length 7.1 cm
> AND Sensor B observed the bar to have length 6.8 cm" is not
> contradictory. (08)
I certainly agree with the following point, which is true, even
with all the normal assumptions about ontology, science, etc: (09)
> It is essential that observations be identified as observations
> and not as statements about the entities being observed. It is also
> essential to say something about who or what is doing the observing
> and about the conditions under which the observation occurs (e.g.,
> accuracy of sensors A and B under various lighting conditions;
> lighting conditions at time of observation; etc.). Of course, this
> information may be unavailable. In this case, it is all too common
> to say nothing about potential observational error, and for the
> consumer to simply assume the observation is perfectly accurate.
> This often generates contradictions. (010)
John (011)
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