Realism Substantial

Do the kinetic rate constants and rate laws apply well to the system being studied Using kinetic rate laws to describe the dissolution and precipitation rates of minerals adds an element of realism to a geochemical model but can be a source of substantial error. Much of the difficulty arises because a measured rate constant reflects the dominant reaction mechanism in the experiment from which the constant was derived, even though an entirely different mechanism may dominate the reaction in nature (see Chapter 16). 

Pollutant realism Is achieved when the test system Includes sufficient diversity of components and the physical and chemical properties so that the pollutant behaves In the test system as it would In nature. Pollutant realism Is lacking because, In most test protocols, the pollutant does not Interact with any part of the environment, except the organism. A lack of pollutant realism In traditional tests may result In overestimates of risk. As an example, substantial Information Is now available about the toxicity of TCDD to numerous species when they are exposed via Injection, Incubation, diet, or dermal application. At Times Beach, Missouri, the TCDD is In the soli, and because It has apparently been there for some time, It is probably tightly bound to the soil. Little Is published about the toxicity of TCDD bound to soil, for any means of exposure. Intuitively, I suspect the TCDD Is less toxic when bound to soil than In the forms commonly used In toxicity testing. Thus, the risks of TCDD-lnduced toxicity to humans at Times Beach may be much smaller than would be suggested by the results of traditional testing which lacks this aspect of pollutant realism. 

Besides, metaphysical realism does not fare any better in practice. In real life, the question concerns the adequacy of particular conceptual schemes. Suppose there are two competing conceptual schemes in a given domain. Which one is right The idea of a mind-independent structure is of little help here. The advocates of the two schemes claim that it is their own scheme that captures that structure. But they have only epistemic criteria to substantiate their claims. Adequacy - in the metaphysical realist view - is completely non-epistemic, so there might be no way of knowing which scheme is adequate. To say that one of the schemes is adequate but we do not know which one leaves the situation completely symmetrical. To put it differently,... 

The dream of realism views the trajectory prospectively as the unfolding of a given substantial reality. Metaphysical realists would claim that Tasmania always was what it is, that it was merely discovered and has not substantially changed from the time when it was completely unknown and void of any specified characteristics, to today when it is articulated in great detail. Latour and the metachemistry of science consider a peculiar obsession this attempt to insist that modern tasmania is identical to the eternal timeless substance that, on the dream of realism, must have been there all along.32 One can understand this obsession if one understands that for the metaphysician the timelessness of substances serves as the foundation of the real and that, therefore, the denial of this identity would cast us into the abyss of relativism and deprive us of all reality (cf. Latour 1999, 3-9, 296). 

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