Models and Idealizations in Quantum Chemistry: The Case of the Born-Oppenheimer Approximation

Abstract

In the context of the idealization discussion, the present chapter aims at two different but complementary objectives. Firstly, we will analyze different kinds of classifications of idealizations that the philosophical literature has proposed during the last decades. The purpose of this review is not merely analytical but mainly programmatic. This means that the goal is not pointing out that a certain classification is incomplete or insufficient, but rather arguing that, in general, an essential feature of idealizations has not been considered. Secondly, we will consider the Born-Oppenheimer approximation (BOA); we will argue that strictly speaking, it is an idealization. Based on the previous review of the recently proposed classifications, we will consider what kind of idealization the BOA is. A detailed analysis of this case will allow us to show the limits of the traditional classifications and, fundamentally, to introduce a new classificatory criterion that we consider indispensable to understanding the scope and the aspiration of quantum theory in chemical practice.