In Minimal Rationality, Christopher Cherniak boldly challenges the myth of Man the the Rational Animal and the central role that the "perfectly rational...

A tacit and highly idealized model of the agent's memory is presupposed in philosophy. The main features of a more psychologically realistic duplex (orn-plex) model are sketched here. It is argued that an adequate understanding of the rationality of an agent's actions is not possible without a satisfactory theory of the agent's memory and of the trade-offs involved in management of the memory, particularly involving compartmentalization of the belief set. The discussion identifies some basic constraints on the organization of knowledge (...) representations in general. (shrink)

Combinatorial network optimization appears to fit well as a model of brain structure: connections in the brain are a critically constrained resource, hence their deployment in a wide range of cases is finely optimized to “‘save wire". This review focuses on minimization of large-scale costs, such as total volume for mammal dendrite and axon arbors and total wirelength for positioning of connected neural components such as roundworm ganglia (and also mammal cortex areas). Phenomena of good optimization raise questions about mechanisms (...) for their achievement: the examples of optimized neuroanatomy here turn out to include candidates for some of the most complex biological structures known to be derivable purely from simple physical energy minimization processes. Part of the functional role of such fine-tuned wiring optimization may be as a compact strategy for generating self-organizing complex neuroanatomical.. (shrink)

At the global as well as local scales, some of the geometry of types of neuron arbors—both dendrites and axons—appears to be self-organizing: Their morphogenesis behaves like flowing water, that is, fluid dynamically; waterflow in branching networks in turn acts like a tree composed of cords under tension, that is, vector mechanically. Branch diameters and angles and junction sites conform significantly to this model. The result is that such neuron tree samples globally minimize their total volume—rather than, for example, surface (...) area or branch length. In addition, the arbors perform well at generating the cheapest topology interconnecting their terminals: their large-scale layouts are among the best of all such possible connecting patterns, approaching 5% of optimum. This model also applies comparably to arterial and river networks. S1063-651X 99 16205-6.. (shrink)

A philosophically important but largely overlooked cognitive theory is examined, one that provides information on which inferences an agent will make from his beliefs. Such a theory of feasible inferences is indispensable in a complete cognitive psychology, in particular, for predicting the agent's actions on the basis of rationality conditions and attributed beliefs and desires. However, very little of the feasibility theory which applies to a typical human being can be shown a priori to apply to all agents. The logical (...) competence required of a rational agent seems to have a cluster structure: it cannot be the case that an agent is able to make no inferences, but an agent can be unable to make any particular one. (shrink)

How things were a decade ago: The largest rain forest of our planet abides in the Amazon Basin, a tenth of the entire world biomass. It is one of the last great frontiers on earth; only the bottom of the sea presents terra incognita on so rich and grand a scale. Perhaps half the planet's species dwell in Amazonia, most of them still unknown to our own technological encampment. No mere ocean of green, this community is so intricately interwoven as (...) to constitute a single vast organism, the one true Leviathan, outweighing all the whales in all the oceans of the world that have ever lived. It is the last and greatest forest on earth, and now it is disappearing before it has been discovered: At nearly an acre a second, the TransAmazon highway system and the land clearing operations it has enabled are extinguishing the forest before it can be explored. From space, Landsat pictures show the burned-over patches spreading with the highway network year by year, magenta sores in the false-color images. We, the voracious Lilliputians now, antlike, are dismantling the greatest biochemical engine on earth at a scale so vast that the carbon dioxide economy of the entire planetary atmosphere suffers. In a century of genocides, perhaps the penultimate great extinction unfolds, prologue to the threatening self-immolation of our own species. (shrink)