Theoretical entities

An important conceptual, or even philosophical, difference between the orbital/wavefunction methods and the density functional methods is that, at least in principle, the density functional methods do not appeal to orbitals. In the former case the theoretical entities are completely unobservable whereas electron density invoked by density functional theories is a genuine observable. Experiments to observe electron densities have been routinely conducted since the development of X-ray and other diffraction techniques (Coppens, 2001).18... 

Our verbal labels have the same ambiguity. When the teacher talks of hydrogen or oxygen she may be talking about the element (as a theoretical entity that is in some sense conserved in reactions although being incorporated in different compounds) the substance or an atom or molecule ... 

As a result, the limited ability of unit processes to create a viable niche for themselves within chemical engineering must ultimately be understood in terms which also involve unit operations. Although the historical resilience of unit processes turned out to be less than that of unit operations, it was no different in its essential elements. Studying the uneasy and ultimately unsuccessful career of unit processes can therefore be easily justified as a way to shed light on the far more successful career of unit operations. In particular, the career of unit processes raises a hypothesis about the evolution of unit operations. The staying power of unit operations was not so much because of the structural coherence of its conceptual elements as its essential links with social and, more specifically, professional groups. As a theoretical entity, unit operations appears far less stable and, in fact, appears quickly threatened by notions which rest on fewer and more fundamental scientific concepts. Ultimately, this threat came to be realized with the advent of transport phenomena, but this is another story. In effect, unit processes can be interpreted as both the attempt to extend the reach of unit operations and a symptom of their conceptual fragility. 

Concepts may have quite an independent life. Relativity was a purely theoretical entity before the first measurement confirmed the idea. Of course, we need experiments to solidify our mental constructs but we do not need experimental proof if there are... 

Pauling s resonance theory raised questions as to the ontological status of theoretical entities very similar to the problematique associated with discussions about scientific realism. Differences in the assessment of the methodological and ontological status of resonance were the object of a dispute between Pauling and Wheland, who worked towards the extension of resonance theory to organic... 

Zeidler, Pawel, Sobczynska, Danuta. 1995—96. "The Idea of Realism in the New Experimen-talism and the Problem of the Existence of Theoretical Entities in Chemistry." Foundations of Science, 4 517-535. 

Vernadsky provides each theory with a specific terminology, postulates laws and makes predictions (retrodictions) based on this theory. The three theoretical entities together compose an all-embracing theoretical system which represent the totality of natural, social and cultural processes on Earth as one single plarietary process. 

Arahatzis, T. 2006. How the electrons spend their leisure time the chemists perspective. In Representing electrons. A biographical approach to theoretical entities, 175-199. Chicago University of Chicago Press. 

Operation Vector expression Corresponding set theoretic entities ... 

The recent dramatic claims made in Nature magazine to the effect that atomic orbitals have been directly observed fly in the face of conventional wisdom regarding the nature of such theoretical entities. Of course this alone does not represent grounds for dismissing such claims. However, if these claims were to be sustained it would imply an outright refutation of quantum mechanics, which does not appear to be the intention of the authors concerned. 

The atomist, by contrast, disputes this on the basis of an appeal to unobservable theoretical entities ... 

At first glance, chemistry seems to deal much more with real things than does physics. Accordingly, most chemists and several philosophers of chemistry tend to take a more or less realist point of view of science. While chemists are usually naive realists, and talk about what some philosophers consider theoretical entities (like atoms, electrons, and even orbitals) as if these had the same epistemological status as apples, spoons, and snooker balls, some philosophers of chemistry have developed a more sophisticated entity realist position (like the dualistic, transcendental realism), or that of a microstructuralist approach. ... 

Arabatzis, 2006] T. Arabatzis. Representing Electrons A Biographical Approach to Theoretical Entities. Chicago Chicago University Press, 2006. 

Yet realism about atoms and molecules was once the central issue for the philosophy of science. Far from being a local problem about one kind of entity, atoms and molecules were the chief candidates for real (or merely fictional) theoretical entities. Many of our present positions on scientific realism were worked out then, in connection with that debate. The very name scientific realism came into use at that time. ... 

In this philosophical approach, therefore, action comes first, before conceptualization, nomenclature or theory. It is tempting to qualify this position as instrumentalism , but this term has already been applied to the philosophical approach championed by Pierre Duhem that interprets theories as conventional tools for calculation or classification without making any claims concerning the reality of the theoretical entities they deploy. What counts is that the classification works without any further concern as to the constructive pay-off in the world. This classic instrumentalism is an anti-realist (or at least anti-scientific-realist) stance that treats its concepts as constructs of the human mind without any referent in the real world. 

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