Search

There is a certain metaphor that has enjoyed tremendous longevity in the evolution of ageing literature. According to this metaphor, nature has a certain goal or purpose, the perpetuation of the species, or, alternatively, the reproductive success of the individual. In relation to this goal, the individual organism has a function, job, or task, namely, to breed and, in some species, to raise its brood to maturity. On this picture, those who cannot, or can no longer, reproduce are somehow invisible to, or even dispensable to, the evolutionary process. Here, I argue that the metaphor should be discarded, not on the grounds that it is a metaphor, but on the grounds that this particular metaphor distorts our understanding of the evolution of ageing. One reason the metaphor is problematic is that it frames senescence and death as nature’s verdict on the value of older individuals. Instead, we should explore a different metaphor: the lengthy post-reproductive period in humans and some other animals is not an accident of culture, but designed by nature for the purpose of supporting and guiding younger generations. On this alternate picture, different stages of life have their own evolutionary rationales, their distinctive design features, their special mandates.

Why do some organisms rely on mental representations for making decisions? Why don’t we rely merely on direct mappings from perception to behavior? Armin W. Schulz’ book, Efficient Cognition: The Evolution of Representational Decision Making, offers a novel and empirically-informed perspective on a problem that has not received the amount of philosophical attention it deserves. In his view, representational decision making evolved because creatures that use it have enhanced cognitive and neurological efficiency. Here I provide an overview of the book’s contents and a critical assessment of his proposal.

I develop a distinction between two types of psychological hedonism. Inferential hedonism (or "I-hedonism") holds that each person only has ultimate desires regarding his or her own hedonic states (pleasure and pain). Reinforcement hedonism (or "R-hedonism") holds that each person's ultimate desires, whatever their contents are, are differentially reinforced in that person's cognitive system only by virtue of their association with hedonic states. I'll argue that accepting R-hedonism and rejecting I-hedonism provides a conciliatory position on the traditional altruism debate, and that it coheres well with the neuroscientist Anthony Dickinson's theory about the evolutionary function of hedonic states, the "hedonic interface theory." Finally, I'll defend R-hedonism from potential objections.

This chapter focuses on the fitness-contribution theory of function, which holds, roughly, that the function of a trait consists in its typical contribution to the fitness of the organisms that possess it. I begin by surveying several different theories within this family, and I show why any plausible version must include a statistical element. I then pose three questions that any proponent of the fitness-contribution theory must answer. First, is fitness a relative notion? When one says a trait “contributes to fitness,” is one saying it contributes to fitness better than some alternative? If so, when we attribute a function to a trait, how do we specify the relevant alternatives? Second, is fitness relative to specific environments? If so, then when we attribute a function to a trait, how do we specify the relevant environments? Third, what precisely must a trait contribute to in order to have a function? Is it survival, reproduction, inclusive fitness, or something else? I then critically assess a major argument in its favor, namely, that it coheres well with the way biologists actually use the term. I consider three different interpretations of this claim and I argue that it does not, in fact, provide an advantage over the selected effects theory in this regard. I close by considering how well it satisfies the adequacy conditions set out in Chap. 1. Theorists disagree about whether the fitness-contribution theory can make sense of the explanatory and normative aspects of function and I survey those disagreements.

In this chapter, I consider three theories of function that are relatively new, in the sense that they have been developed over the last twenty years. The “weak etiological theory” says, roughly, that a trait token in an organism has a function so long as that kind of trait contributed to the fitness of that organism’s ancestors and it is inherited. It defines function in terms of inheritance and past contributions to fitness, but not selection. I assess some differences between this theory and the standard selected effects account and question the motivation for the account. A second group of theories is known as the “systems-theoretic” or “organizational” view. This is not a single theory but a family of theories based on the idea that a trait token can acquire a function by virtue of the way that very token contributes to a complex, organized, system, and thereby to its own continued persistence, as a token. I argue that the organizational approach faces liberality problems. Finally, the modal theory of function holds that the function of a trait token has to do with the behavior of that token in certain nearby possible worlds. I assess the theory and survey some problems. Bence Nanay developed the modal theory as an attempt to solve a certain circularity problem that he believes afflicts most other theories of function, but it is not clear whether there is a real problem here to be resolved.

This chapter focuses on the selected effects theory of function. According to this view, a function of a trait is whatever it was selected for by natural selection or some natural process of selection. I show how the theory plausibly accounts for the explanatory and normative aspects of function. First, if a function of a trait is whatever it was selected for by natural selection, then when one attributes a function to a trait one provides a causal explanation for why the trait currently exists. Second, since the function of a trait is determined by its history rather than current performance, it is easy to see how a trait can have a function that it cannot perform (“dysfunction”). I sketch the somewhat complex historical background of this theory. The theory was actually developed by biologists throughout the twentieth century, and in the 1970s philosophers began to explore it systematically. I survey the major criticisms of the theory and show why they are not compelling. Critics say that it does not really account for the explanatory and normative features of function; that it is inconsistent with the way biologists actually use the term; that there are (real or imaginary) counterexamples; and that it is committed to adaptationism. I close by presenting a new version of the theory, the generalized selected effects theory, which shows how brain structures (such as synapses) can acquire new functions during an individual’s lifetime through a process that is analogous in some ways to natural selection itself.

Scientists, philosophers, and even the lay public commonly accept that schizophrenia stems from a biological or internal ``dysfunction.`` However, this assessment is typically accompanied neither by well-defined criteria for determining that something is dysfunctional nor empirical evidence that schizophrenia satisfies those criteria. In the following, a concept of biological function is developed and applied to a neurobiological model of schizophrenia. It concludes that current evidence does not warrant the claim that schizophrenia stems from a biological dysfunction, and, in fact, that unusual neural structures associated with schizophrenia may have functional or adaptive significance. The fact that current evidence is ambivalent between these two possibilities (dysfunction versus adaptive function) implies that schizophrenia researchers should be much more cautious in using the ``dysfunction`` label than they currently are. This has implications for both psychiatric treatment as well as public perception of mental disorders.

The Harvard physiologists Alexander Forbes (1882-1965) and Walter Bradford Cannon (1871-1945) had an enormous impact on the physiology and neuroscience of the twentieth century. In addition to their voluminous scientific output, they also used literature to reflect on the nature of science itself and its social significance. Forbes wrote a novel, The Radio Gunner, a literary memoir, Quest for a Northern Air Route, and several short stories. Cannon, in addition to several books of popular science, wrote a literary memoir in the last year of his life, The Way of an Investigator. The following will provide a brief overview of the life and work of Forbes and Cannon. It will then discuss the way that Forbes used literature to express his views about the changing role of communications technology in the military, and his evolving view of the nervous system itself as a kind of information-processing device. It will go on to discuss the way that Cannon used literature to articulate the horrors he witnessed on the battlefield, as well as to contribute to the philosophy of science, and in particular, to the logic of scientific discovery. Finally, it will consider the historical and philosophical value of deeper investigation of the literary productions of scientists.