Greg Detre
Monday, 5th November, 2001
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Nagel defines rationality as the capacity �to recognise objectively valid reasons and arguments�. He is a realist about reason and does not want to accept reductive interpretations of it is as a �contingent though basic feature of a particular culture or form of life�. He recognises that he needs to address the question of how it is that contingent, biological creatures such as ourselves can have access to such universally valid methods of objective thought. I want to focus on the extent to which evolutionary theory supports or undermines such rational objectivism, as I will term Nagel�s position.
The fundamental tenet of evolutionary theory (or �neo-Darwinism�) is the principle of natural selection, whereby parental characteristics that vary across organisms play a role in non-random differential reproduction. That is, �adaptive� variations (i.e. enhance �fitness�) are those which increase an organism�s (probabilistic) propensity to survive and reproduce. This process gradually gives rise to diverse forms leading ultimately, through selective adaptation to specific niches and environments, to the emergence of new species. If humans are the end-product of a natural, non-teleological process of evolution that has resulted in the particular, contingent bodies and brains that we have, then our reasoning abilities and limitations will be explicable in terms of evolutionary theory too.
Curiously, evolutionary theory has been employed by both objectivists and subjectivists to support their claims. For example, Stich cites Quine, Dennett and Fodor as implying that evolution selects for rationality and that irrationality is empirically impossible or unlikely, e.g.:
creatures inveterately wrong in their inductions have a pathetic but praiseworthy tendency to die out before reproducing their kind.[1]
Yet, Pinker and others have argued that the opposite is the case, i.e. that evolved creatures (including ourselves) are highly unlikely to be rational. I will start by reviewing how objectivists try and use evolutionary theory to directly support their claim, and then consider how it can also be employed by the subjectivists. Even though I think that the empirical psychological and biological evidence clearly undermines the objectivists, Nagel argues that such evidence belongs to the family of arguments that can be attacked as self-defeating. Unfortunately, if we accept his argument, he leaves us in a position analagous to the �explanatory gap� in philosophy of mind, where hard science is unable to incorporate how things clearly seem to us to be into its explanation.
Stich considers that there are two main reasons why people think that evolution insures rationality:
He systematically takes apart both of these premises. His aim is not to demonstrate conclusively that evolution theory is incompatible with rational objectivism, but merely to show that the rational objectivists have their work cut out in showing how the two can sit together. I will not consider the arguments in as much detail, but I will try and recount, evaluate and supplement them to a limited extent.
The notions of �fitness� and �optimality� are central to any evolutionary theory. A system is �well-designed� if it enhances biological fitness (likelihood to survive and reproduce successfully) more than any alternative. Of course, this is problematic because of the difficulties of deciding what counts as an alternative. No doubt a predator which had evolved a high velocity rifle as an extra limb would be at an enormous evolutionary advantage, but as I will discuss below, the march of evolution is restricted to a sequence of gradual changes, each adaptive in their own right � although the end result of a fully-functional rifle would be highly adaptive, all of the intermediary stages (growing a long, perfectly straight, protruding barrel, the combustion mechanism, an organ for ammunition manufacture etc.) would be highly maladaptive right up until they were all brought together.
Stich considers a number of technical arguments against a na� faith in evolution as an infallible optimiser. He points out that natural selection is not the only process that causes changes of gene frequency in populations (which is how biologists define evolution). Mutation, migration and random drift all affect gene frequencies, to a greater or lesser degree. For instance, a random event or disaster might wipe out a large proportion of a population, including all the carriers of a particular fit gene, allowing a less fit gene to take hold in the population.
Natural selection does not necessarily choose the best genes in the gene pool anyway � Stich discusses meiotic drive, the effect of combined recessive genes, pleiotropy and heterozygote superiority. Each of these phenomena can lead to less optimal members of the available gene pool being selected for. In the case of meiotic drive, for example, �certain genes have the capacity to �cheat� in meiosis [�the process that produces sperm and eggs�] and end up significantly over-represented in the sperm or eggs�, and so �obviously, such a gene will spread quickly through a population, even if the phenotypic effects of the gene are harmful�.
I would like to emphasise a deeper problem about evolution for objectivists that Stich touches on. Evolution is not teleological � it does not modity towards an end-goal, but by producing various slightly different incarnations, each one a little bit more or a little bit less adaptive than its parents. Most modern biologists are gradualists, that is, they believe that a host of these tiny changes amount to large-scale improvements in the organisms, like a new organ. In contrast, saltatory explanation holds that sudden, marked �leaps� (macro-mutations) drive evolution forwards. Assuming the gradualists to be correct, evolution suffers from what artificial intelligence researchers term the �hill-climbing problem�. In outline, this considers that the space of possibilities which evolution is exploring through natural selection working on population variation can be visualised as a landscape, in which the hills and mountains represent more optimal designs. If the mechanism of evolution progresses incrementally, visualisable as travelling in a continuous path uphill, then a population may become stranded on a nearby hill, unable to traverse to the nearby mountain (an optimal design) which is separated by a valley.
Nagel rightly states that �the essential characteristic of reasoning is its generality�.[2] Nagel is certainly not content to regard his rational capacity as forming beliefs that are merely relative, true for a New Yorker, true for an American, true for a human even. He seeks to defend reason as a universal source of authority. In order to do that, surely our inferential system needs to have evolved to be absolutely optimal. If it was merely very well-designed, it might be able to generalise well, but not generalise to �objectively valid� conclusions. Its conclusions might be much less subjective than a less well-designed system, but still not entirely generalisable. Given how unlikely it is that any evolved system is ever wholly optimal, does this mean that we there is no hope that we could be rational in the way that Nagel envisages? I think that the answer to this is probably �no�. In the discussion above, Cherniak showed that there is a scale of rationality, and that Nagel�s requirements for objective rationality place him at the high end, but not the top of that scale, requiring a high level, but not maximum, optimality.
Lastly, it is necessary to show that our cognitive system is a product of biological evolution. After all, �even if it were the case that natural selection is a flawless optimiser and that it is the only cause of biological evolution, it would still not follow that our system of inferential strategies is optimally well-designed� unless �evolutionary factors are the only [or major] ones that have shaped our current inferential strategies�. In order for natural selection to shape a characteristic, there must be variation in the population that affects reproductive success in a systematic way, and this variation must be under genetic control either directly or indirectly. He considers clothing styles and language as examples in which there is great diversity within the human population, that may have some impact on fitness, but this diversity is not genetically based. �Had I been born elsewhere, I would now have the ability to speak Lapp or Korean rather than English.� And the processes by which languages spread are almost entirely independent of biological evolution, depending far more on social and historical factors, for example. Similarly, it may be that �the [inferential] strategies a person employs, like the language he/she speaks, are determined in large measure by environmental variables�.
Assuming that the objectivist could show that evolution produces near-optimal systems, the crucial second step necessary to show that evolution selects for rational systems is to show that an optimal system is a rational one.
Analytic epistemology is the approach of analysing our ordinary concepts
why
are/would be optimal systems rational?
optimality
is conceptually reducible/identical to rationality (analytic epistemology)
this is
implausible � why???
see
Stich�s later arguments against analytic epistemology generally
having
true beliefs is more adaptive
a
system that produces true beliefs may be more expensive (than it�s worth)
a
system that produces true beliefs may be worse for survival than rules of thumb
that sometimes get things wrong but are less likely to get us killed, say
e.g.
Euclidean geometry (does this work, given that the reason that we have
Euclidean geometry probably has less to do with our inferential system than our
perceptual system, and the fact that at the level of the universe within which
we operate, it is a more or less Euclidean world)
see
Nozick (self-evidence)
Nozick�s account supplements Stich�s arguments nicely. He sees the relationship between evolution and rationality as informing problems aired by Descartes and Hume. Hume�s problem of induction addressed the impossibility of finding a rational (deductive) argument for why (inductive) reasoning works. Descartes questioned why self-evident propositions, as discerned by the natural light of reason, must correspond to reality.
After all, if reason and the facts are independent variables, why should they be correlated at all? Kant responded that since we cannot show why our reason would conform to objects, it must be that we perceive the objects to be the way they are because they are constructed by our faculties. In other words, our knowledge is not of things in themselves, but only of an empirical reality shaped by our constitution. Kant termed this upheaval a �Copernican revolution�, although confusingly, in contrast to Copernicus� effect on astronomy, Kant is reaffirming an anthropomorphic perspective on the universe.
Nozick is
overturning the Kantian dependence of the facts on reason. His �evolutionary hypothesis� amounts to
saying that it is reason that is the dependent variable, shaped by the facts. Our
inferential system has evolved to become specialised for common past situations
and stabilities in our environment. He suggests that there was selection for
recognising as valid certain kinds of connections that are factual, which come to
seem to us as more than just factual. Thus, the neural architecture for a given
factual connection that appears regularly and stably in our environment may be
modified over evolutionary time so that our descendants learn it faster.
Thus, �reason tells us about reality, because reality shapes
reason, selecting for what seems �evident��. However, just because a certain factual connection has been consistent
in the past and we have evolved to see it as a vaild and increasingly
self-evident basis for inference, does not guarantee that it will continue to
hold in the future. Moreover, the question is not just whether the
stable regularities of the past continue to hold in the future, but also
whether evolution has picked out the �right� regularities or given us �green�
in a �grue� world. We may come to see
the given sequence of thought as increasingly self-evidently certain (because
we are selected to do so, because in a stable world such semi-automatic
inference-making is adaptive), but this does not guarantee that it ever was
strictly true.
Importantly then, he is not saying that it is the capacity
to recognise independently existing valid rational connections that is selected
for. Rationality can be seen as a biological adaptation with a function. It was
never the function of rationality to justify certain of our most basic, stable,
useful assumptions, because all we needed was to utilise them as trust-worthy,
predictive regularities. These basic, sub-rational assumptions include the list
of philosophical problems we�ve been least successful with: the problems of
induction; of other minds; of the external world; and of justifying rationality.
It initially seems as though this wholly undermines any claims to objectivity through reason, though in fact Nozick is keen to defend against seeing this as the consequence of his arguments.
We may still be able to sharpen our goals and procedures though, at least to some extent. Evolutionary theorising may help us understand what sort of rational system would be adaptive, and consequently why our rational system is the way it is. The fact that rationality wasn�t designed to justify itself or its framework assumptions does not mean that it can�t, or that we can�t turn our rationality upon itself.
Rationality is self-conscious,
in that it attempts to correct biases in the information it is supplied, and in
its processes of reasoning. Nozick claims that �Whatever the initial functions
of reasons were, we can use our ability to employ reasons to formulate new
properties of reasons and to shape our utilisation of reasons to exhibit these
properties. We can, that is, modify and alter the functions of reasons, and
hence of rationality.�
After all, although psychological experiments show how often
most people fail to reason well, for example about probability, the very fact
that we have been able (through centuries of reflection) to formalise and so
correct such faulty reasoning lends hope to improving upon these biologically-instilled assumptions,
e.g. Euclidean geometry.
However, Nozick is stresses that his evolutionary account of why we find certain thought processes rationally self-evident does not provide a reason-independent justification of reason. Rather, it is part of our current, ongoing scientific view, and not part of first philosophy.