Does human nature determine human culture, or does our culture shape our nature? This edited volume responds with an emphatic “Both/And!” (pp. 1, 3, 17, 101, 154, 188, 201–2, 301–2). Yes, our evolutionary inheritance, genetic composition, and neurological structures significantly impact our sociopolitical attitudes, beliefs, values, and behaviors. And yes, the cultural environment affects the way human nature unfolds, triggering genetic expression, eliciting physiological disposition, and likely influencing their evolution. This interaction of nature and culture, biology and environment, editors and contributors maintain, provides one of the most promising, interesting, and underexploited fields of inquiry for political scientists today.

To this interactionist endorsement the editors add a warning. Political scientists do their profession a great disservice if they refuse to integrate insights from the life sciences. The discipline will become a biologically illiterate child scorned by its faster maturing social science siblings. There is a moral lapse involved as well, the editors assert, if political scientists do not investigate in transparent fashion and in accord with scientific standards the biological influences on human behavior that governmental and corporate actors are already exploiting—potentially for nefarious purposes.

I embrace the endorsement and the accompanying warning. Political scientists have much to learn from, and to contribute to, the life sciences. But there are notable absences in the volume that diminish its contribution to the field, narrow its range of interest, and weaken its normative position.

Notwithstanding the oblique reference to Aristotle in its title, the volume accords the ancient philosopher only a single, passing remark. No entry for Aristotle exists in the index, and he fails to appear in any reference sections. There are likely two reasons for this omission. The first reflects on discoveries in evolutionary biology and neuroscience and will be addressed in the final paragraphs of this review. The second is the common perception that science, as a cumulative and progressive intellectual enterprise, has long ago left its early practitioners behind. Just as physicists and zoologists no longer study Aristotle, notwithstanding his seminal contributions to these fields, so political scientists—especially those courting the “harder” sciences—might deem it a sign of immaturity to dwell upon intellectual ancestors. A polite bow suffices.

Whatever the reason, the omission is unfortunate. And it is symptomatic of a larger problem. No chapters address political philosophy or theory. This weakens the volume in at least four ways.

First, the editors' assertion that political scientists have an ethical obligation to explore the biology of human behavior is left wholly unsubstantiated. Some fleshing out of the claim would be in order, and the likely candidate for the job is a political theorist. Second, the volume would have benefited from the replacement of any of its many chapters detailing how political scientists can utilize biological knowledge with at least one account of how biological scientists utilize philosophical knowledge. There is no shortage of material here. Some of the most influential neuroscience in recent years, for example, has been grounded on the same philosophic writings that occupy political theorists.Footnote ¹

Third, the editors might have included a chapter that summarizes natural scientific disconfirmations of political thought. For example, Antonio Damasio, a neuroscientist, has employed extensive empirical data to disconfirm Descartes's famous mind–body dualism in Descartes' Error (Reference Damasio1994). There are important ramifications of this disconfirmation for political philosophy and political science. In turn, Steven Pinker, an experimental psychologist, has recently demonstrated that Thomas Hobbes was right and Jean-Jacques Rousseau was wrong regarding at least one key point of disagreement between them.

Hobbes famously declared that the state of nature was a state of war of all against all, making our ancestors' lives “solitary, poor, nasty, brutish and short.” In contrast, Rousseau insisted that the noble savage seldom knew conflict. His (simple) needs were easily sated in the state of nature, and so there was no reason to battle over resources. Pinker demonstrates that violence was standard fare for early humankind, but that it has markedly decreased over time. Contradicting popular claims of the unprecedented level of violence of the twentieth century—with its two world wars, multiple regional wars, and totalitarian decimations—Pinker observes in The Better Angels of Our Nature that on a per capita basis, humankind is ever more peaceful.Footnote ² Notwithstanding isolated periods with high levels of murder and organized conflict, the overall trend is clear: Our species is becoming increasingly nonviolent as a product of its ever more civil(ized) existence. The life sciences help explain why.

The fourth absence is, to my mind, the most problematic. The volume is dedicated to exploring the ways in which political phenomena are shaped by our inner (genetic, evolutionary, and neurological) nature. Unfortunately, it neglects a two millennia–old tradition of examining our inner nature and how it is shaped by political phenomena. Plato was only the first of a long line of philosophers to explore the politics of the soul. Soulcraft and statecraft were inherently related, Plato insisted, because the soul itself was a polis of sorts. In the Republic, Socrates declares that the man of wisdom chiefly minds the “constitution” not of his country but of his soul, the city-state within himself.Footnote ³ The relationship between statecraft and soulcraft has been an enduring concern for political theorists ever since. Even philosophers who vehemently reject Plato's idealism, such as Friedrich Nietzsche, have focused on the dynamics of our inner politics—a multiplicity of competing drives, each vying for hegemony.Footnote ⁴ Unfortunately, this volume offers no investigations of the ways our inner constitutions are formed, or how they get amended.

To address this unfortunate lapse—and to give the title of their volume a little more weight—the editors might have included a chapter on the relationship between neuroplasticity and Aristotle's understanding of our inner constitution. Although it gains no attention by editors or contributors, the plasticity of the brain is an area of increasing interest to life scientists. It refers to the brain's capacity to adapt and remodel itself in response to environmental demands, experiences, and trauma. Scientists now acknowledge that neuroplasticity, previously believed to be limited to young children, is regularly evidenced in adults. Brain imaging technology, such as MRIs and PET scans, demonstrates that our “neural architecture is not a fixed structure.”Footnote ⁵

The adult brain manifests plasticity in various ways: Synaptic linkages become stronger or weaker, the generation and release of neurotransmitters and hormones are altered, neurons and neural connections that are underutilized get pruned, and new synaptic connections as well as entirely new neurons develop. Neuroimaging of London taxi drivers, for instance, demonstrated growth in the posterior of the hippocampus proportionate to the number of years the cabbies navigated the city. Most neurogenesis in adults, studies suggest, is associated with the hippocampus, and in particular the region of it known as the dentate gyrus, where new memories are formed.

Learning reflects the development and reinforcement of neural pathways in the brain and, oftentimes, the co-optation of pathways that are underutilized. As Joseph LeDoux observes: “[S]ynapses in the brain, like animals in their environments, compete to stay alive. Synapses that are used compete successfully and survive, while those that are not used perish.”Footnote ⁶ The brain's linkages develop by way of a process akin to natural selection. A neural Darwinism is at play, and the law of the synaptic jungle is “survival of the busiest.”Footnote ⁷ Neurons that frequently interact will survive. The rest atrophy or are co-opted. As brain scientists observe, intoning what is commonly know as Hebbian plasticity: “Cells that fire together, wire together.” When synaptic events (firing together) become synaptic probabilities, structural change (wiring together) is at hand.

An even more robust sense of brain plasticity occurs in neurogenesis, when wholly new neurons grow. The London cabbie example demonstrates how the mental activity of memorizing and recalling the names and geography of city streets can have this effect. Studies indicate that voluntary physical exercise also increases the number of new neurons that form in the hippocampus. Environmental stimulation may then help these new cells to survive and become dominant—by keeping them busy. From an evolutionary point of view, this phenomenon would have obvious benefits, rewarding the physical exploration of new environments with enhanced learning capacity.

The brain is regularly remodeled by experience. As self-conscious creatures, however, much of what we experience occurs within our own minds, the product of mental activities. Important, then, is the role of self-consciousness in “cortical remapping.” A self-reflective mind within a nutritive environment can significantly modify its own brain structures and functions. Shifting your thoughts can reshape your brain. In turn, reshaping your brain alters your behavior, which impacts ongoing brain function and structure. A virtuous (or vicious) cycle may form. It is easy to exaggerate the human capacity for neural remodeling. Still, to no small degree we are the architects of our own brains. In this respect, neuroscience can and should inform our ethics and politics.Footnote ⁸

Aristotle brings this point home. We read in the Nicomachean Ethics: “Habit … is practice long pursued, that at the last becomes the man himself.”Footnote ⁹ This, essentially, is Aristotle's habit theory of virtue. Virtues are like any other habits or acquired skills. “The moral virtues we do acquire,” he observes, “by first exercising them. The same is true of the arts and crafts in general.”Footnote ¹⁰ We become virtuous, in other words, by (re)wiring the brain in specific ways through repeated practice. These newly formed brain maps then incline us to certain activities in particular circumstances, and make it easier (both physically and emotionally) to perform these deeds.

Contradicting the teachings of his mentor Plato, Aristotle insisted that the disposition to do the right thing on a regular basis is not a feat of cognitive conviction. Rather, it is an embodied habit grounded in repeated practice. As Aristotle notes, the knowledge that allows for the practice of virtue “must be worked into the living texture of the mind, and this takes time.”Footnote ¹¹ To develop a virtue, we must co-opt neural territory for new purposes and regularly reinforce these synaptic connections. To develop a virtue is to engage in brain sculpting.

Aristotle gave the original “Both/And” statement when articulating his habit theory of virtue: “The moral virtues, then, are produced in us neither by Nature nor against Nature. Nature, indeed, prepares in us the ground for their reception, but their complete formation is the product of habit.”Footnote ¹² Aristotle is saying that nature and nurture, biology and environment, work together at the level of our inner constitution to reconfigure it. Through our actions and thoughts we become, neurologically speaking, certain sorts of people disposed to certain sorts of behavior. The “true moral act,” neuroscientists suggest, is self-conscious brain sculpting.Footnote ¹³ In this respect, a “neuro-Arisotelean” approach to the study of brain plasticity and its relation to human virtues, habits, skills, and dispositions should be of great concern to political scientists.

I promised to speculate as to why Aristotle, and more generally political philosophy, found no place in this edited volume. The reason might have to do with the way the brain itself is structured. Our brains are lateralized. Although the extent and nature of lateralization is often exaggerated and overly simplified in popular literature (as by early neuroscientists), the hemispheres of the brain do specialize. The left hemisphere develops most denotative language functions and syntax. It is where fact retrieval and linear, sequential reasoning, along with many other calculative (mathematical) functions, occur. The right hemisphere learns to recognize faces, interprets speech intonation, and activates metaphoric and poetic thought. It is more densely connected to limbic (emotional) and brain stem (instinctual) functions and plays a dominant role in the learning of new skills.

The right hemisphere specializes in holistic perception, such as pattern recognition, while the left hemisphere is more analytic and detail oriented. In turn, the right hemisphere perceives and accommodates novelty, while the left tends to work within set paradigms. To grossly simplify: The left hemisphere seeks the analytic certainty that allows control, while the right hemisphere discerns the context and fosters the compassion that allows creativity and connection.Footnote ¹⁴

Man Is by Nature a Political Animal demonstrates a predominantly left-brained approach marked by the systematic effort to secure intellectual control through detailed analysis and the use of established quantitative methods. Absent are more holistic meditations that capture contextual significance and meaning. It would be a shame if political scientists, in their haste to integrate the data and adopt the methodologies of the life sciences, forgo the benefits to life—and to their discipline—of well-balanced, whole-brain thinking.