Explaining the Brain: Mechanisms and the Mosaic Unity of Neuroscience

Book Preface

There are neurophilosophers, and there are philosophers of neuroscience. Neurophilosophers use findings from neuroscience to address traditional philosophical puzzles about the mind. Philosophers of neuroscience study neuroscience to address philosophical puzzles about the nature of science. Philosophers of neuroscience are interested in neuroscience because it has distinctive goals, methods, techniques, and theoretical commitments. In this book, I propose a unified framework for the philosophy of neuroscience. Because neuroscience is like other special sciences in many respects, this framework contains lessons for the philosophy of science generally.

I develop this framework by addressing the following question: what is required of an adequate explanation in neuroscience? Debates frequently arise among neuroscientists and philosophers about whether a proposed explanation for a given phenomenon is, in fact, the correct explanation. Does Long-Term Potentiation (LTP) explain episodic memory? Do size differences in hypothalamic nuclei explain differences in sexual preference? Does the deposition of beta-amyloid plaques in the hippocampus explain memory deficits in Alzheimer’s disease? Do 40 Hz oscillations in the cortex explain feature-binding in phenomenal consciousness? While the answers to these questions depend in part on specific details about these diverse phenomena, they also depend on widely accepted though largely implicit standards for determining when explanations succeed and when they fail. My goal is to make those standards explicit and, more importantly, to show that they derive from a systematic and widespread view about what explanations are, namely, that explanations in neuroscience describe mechanisms.

My project is both descriptive and normative. My descriptive goal is to characterize the mechanistic explanations in contemporary neuroscience and the standards by which neuroscientists evaluate them. This cannot be accomplished without attention to the details of actual neuroscience. I illustrate my descriptive claims with case studies from the recent history of neuroscience. For neuroscientists, I present enough detail to make the philosophical views concrete. For philosophers, I limit myself to the details required to demonstrate that the view corresponds to real neuroscience. This descriptive goal helps to keep the philosophical discussion targeted on issues relevant to the neuroscientists building the explanations.

The goal of searching for mechanistic explanations is now woven through the fabric of neuroscience: it is taught through examples in classrooms and textbooks; it is propagated in introductions, discussion sections, and book chapters; and it is enforced through peer review, promotion, funding, and professional honors. To understand contemporary neuroscience, one has to understand this form of explanation. A second reason to pursue this descriptive project is that questions often arise about the adequacy of widely accepted strategies of explanation in neuroscience (see, for example, Uttal 2001; Bennett and Hacker 2003). We can address the question of whether the norms of neuroscience are justified only when we have an idea of what the norms are and of how they can be defended.

The descriptive project, in other words, is the first step in a normative project: to clarify the distinction between good explanations and bad. As the body of neuroscience research continues to expand, it is worth pausing periodically to reflect on the goals of explanation and on the standards by which explanations should be evaluated. Similarly, as neurophilosophers learn more about neuroscience and seek to apply neuroscientific explanations to philosophical problems, they also need to learn to reflect critically on the standards for evaluating the explanations that they adopt. Here the philosopher of neuroscience can help. They can use the long tradition of philosophical literature about the nature of scientific explanation (see, e.g., Salmon 1989) to reveal crucial features of explanation in neuroscience specifically, and they can use neuroscience to reveal previously unrecognized features of explanation across the sciences (or at least the special sciences) generally.