|Abstraction: Subsumption of objects by non-consideration of certain properties. See also equivalence relation, concretion, concreta, indiscernibility.|
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Abstractions/Duhem: E.g. Abstraction of the ordinary mind: Before the thunder is heard, one can see the flash. The concepts are abstract, but the sensory rumbling and twitching is recognizable.
This is no longer the case with the laws of physics.
E.g. at a constant temperature, the volumes occupied by the same gas mass are inversely proportional to the pressures under which they are placed. The notions are not only abstract, but supremely symbolic, and the symbols get a meaning only through the physical theories. The relations are by no means immediate; they are only produced by means of instruments.
Abstraction/Duhem: Difference Physiology/Physics:
E.g. Assumption: the anterior extremities of the spinal cord contain the motor nerve fibers, the posterior the sensory. When he cuts the front end, the mobility of certain parts of the body must cease. The physiologist observes the consequences of his operation and must abstract from all his thoughts on the physiology of the marrow. He must not ignore any move, no twitching that contradicts his prediction. He must not attribute it to any secondary cause. He must establish an absolute separation between the consequences of his theoretical deductions and the factualization of the facts shown by his experiments.
Even if the experimental method (as described earlier) is difficult, the logical analysis is very simple.
This is no longer the case when the theory which is to be subjected to the control of facts is not part of physiology anymore but of physics. Here, one cannot leave the theory which one wants to examine, in front of the door of the laboratory. For without it, it is impossible to adjust even a single instrument, to interpret a single reading. When the physiologist, or the chemist, makes use of instruments, he implicitly assumes the correctness of theories which give the abstract concepts, such as temperature, density, etc., a real meaning by means of which the concrete information of these instruments are translated. But the theories belong to the realm of physics. For all, the expression of the result of the experiment contains an act of belief in a whole group of theories.
Ziel und Struktur der physikalischen Theorien Hamburg 1998