For Carl F. Craver, the philosophy of neuroscience has a labor-intensive and challenging objective to realize and a fundamental truth to reveal.  Its objective is to make explicit the ‘widely accepted though largely implicit standards’ upon which scientists rely to assess the adequacy of explanations of brain phenomena.  The undeniable fact to uncover, Craver claims, is that at present ‘explanations in neuroscience describe mechanisms’.  In Explaining the Brain: Mechanisms and the Mosaic Unity of Neuroscience, the author takes the goal of divulging the standards of neuroscience seriously, methodically dissecting a variety of interpretations of brain phenomena to highlight their underlying similarities and differences and their strengths and weaknesses. Craver also cleverly concentrates on a few key illustrations of mechanistic explanations in neuroscience and then literally disassembles them to expose the norms that define their foundations.  

How can a philosopher of neuroscience uncover the norms that neuroscientists use to distinguish an adequate explanation from an inadequate one?  One practical approach, Craver argues, is to determine the extent to which explanations offer a practical understanding of the functioning of the brain.  Practical knowledge increases scientists’ alleged control over the human brain by guiding the development of targeted interventions.  If this approach sounds rather obvious, other approaches considered by the author are no less so.  Craver mentions studying instances of widely accepted or rejected explanations of brain phenomena and examining the explicit arguments neuroscientists make in support or in opposition to accounts of such phenomena. Can all these approaches, combined, be sufficient to determine not only the nature of the norms that underlie accounts in neuroscience, but also the limits of the mechanistic framework?  The author’s answer is expectedly intricate. Craver painstakingly distinguishes between etiological accounts, for which antecedent events serve as explanations and constitutive accounts, for which the components of a phenomenon serve as explanatory devices.  Within the latter, he differentiates between reductionism whereby the main goal of explanations is to form identities between higher and lower levels of analysis and the system approach whereby the goal is to decompose complex systems into their parts and understand how they function together as a whole.  Craver examines different embodiments of the mechanistic framework, but mainly focuses on reductionism meticulously to highlight its limitations.

Craver’s response to reductionism falls within the system approach and is branded as ‘mosaic unity’.   Unsurprisingly, the ‘mosaic unity’ approach recognizes that neuroscience is comprised of different subfields of knowledge and discovery, each with its own vocabularies, investigative procedures, and theoretical focuses.  The independent working of subfields is key to the ‘mosaic unit’ approach.  Craver proposes that neuroscience acknowledges each subfield’s unique prospective and uses it to judge the plausibility of the mechanisms that may be responsible for a given phenomenon.  If his proposal is implemented, then different levels of analysis can be conceptualized as representing independent means for identifying mechanisms underlying the phenomenon under investigation.   Simply stated, if the hypothesized source is consistent with different and independent levels of analysis, then the source is a plausible account of the phenomenon.  

Craver’s collaborative approach to knowledge acquisition and validation in neuroscience is not merely concerned with the nature and quality of neuroscientific explanations, but it encompasses the key and notoriously contentious issue of how it is best to attain unity in a field defined by diversity.  According to Craver, unity cannot be achieved by scientists’ chimerical search for common methods of formulating and evaluating beliefs.  Similarly, he argues that the reductionist metaphor, whereby accounts of lower-order phenomena (long-term potentiation) are given as explanations for higher-order phenomena (memory), cannot achieve unity in a field overflowing with multi-level phenomena.  His novel proposal is for neuroscience to focus on integrating knowledge from different subfields by using such knowledge to constrain explanations of mechanisms at multiple levels of analysis.  Unity is thus the byproduct of collaboration which requires scientists’ willingness to put theories from different subfields through the rigorous test of ascertaining their coherence across domains of inquiry (e.g., are biological accounts of memory consistent with psychological accounts?).  Generally speaking, Craver’s proposal appears plausible as one that may actually succeed in reducing conceptual fragmentation and disharmony in the field of neuroscience by offering scientists who operate at diverse levels of analysis a workable conceptual framework.

The author suggests that Explaining the Brain is a book for individuals interested in neuroscience, the philosophy of science, and the philosophy of the mind.  I believe this text may most benefit the work of neuroscientists to whom Craver offers the precious gift of self-awareness.  Overall, Explaining the Brain is a complete read of thoughtful revelations of the inner workings of neuroscience intermixed with a few temperate insinuations on how its complex and ostensibly unsystematic workings may be unified.  In summary, Craver’s text is a read which is intense and, albeit slightly redundant, undeniably enlightening. 

© 2010 Maura Pilotti

 Maura Pilotti, Ph.D., Department of Psychology, Hunter College, New York