Setting human limitations...

[Jim__]

5. In your attempt to discuss human limitations you raise 2 spurious issues: fear and religion.

Your post does not justify either issue as pertinent to the consideration of human limitations.

I'm going to consider only the potential limitations on human knowledge. My first consideration in this would be the historical development of the human brain. It developed through evolution via the natural selection of accidental mutations. Specifically, the human brain was selected for because it solved problems in the environment better than brains based on other accidental changes. We have to assume that our brains are a minimal cost model that can work well with our bodies and solve environmental problems a little bit better than the next-best model. Since evolution did not require that our brain have an unlimited capacity to solve problems; but only a slightly better capacity to solve the problems that were encountered in its environment, I believe that there is an a fortiori case that the human brain has limitations.

Is there any evidence for such limitations? Yes. For example, the human brain has a tendency to categorize knowledge. We divide up problems into subject matter categories, entities into life and non-life categories, life into plant and animal, and then subdivide these categories. To a certain extent, we see the world in terms of these categories; they have a certain determinative effect on our knowledge. Is there a physical constraint on the categories that we choose? An excerpt for Philosophy in the Flesh by George Lakoff and Mark Johnson (Basic Books pp 18 - 19):

The first and most important thing to realize about categorization is that it is an inescapable consequence of our biological makeup. We are neural beings. Our brains each have 100 billion neurons and 100 trillion synaptic connections. It is common in the brain for information to be passed from one dense ensemble of neurons to another via a relatively sparse set of connections. Whenever this happens, tha pattern of activation distributed over the first set of neurons is too great to be represented in a one-to-one manner in the sparse set of connections. Therefore, the sparse set of connections necessarily groups together certain input patterns in mapping them across to the output ensemble. Whenever a neural ensemble provides the same output with different inputs, there is a neural categorization.

To take a concrete example, each human eye has 100 million light-sensing cones, but only about 1 million fibers leading to the brain. Each incoming image therefore must be reduced in complexity by a factor of 100. That is, information in each fiber constitutes a "categorization' of the information from about 100 cells. Neural categorization of this sort exists throughout the brain, up through the highest levels of categories that we can be aware of. When we see trees, we them as trees, not just as individual objects distinct from one another. The same with rocks, houses, windows, doors, and so on.

A small percentage of our categories have been formed by conscious acts of categorization, but most are formed automatically and unconsciously as a result of functioning in the world. Though we learn new categories regularly, we cannot make massive changes in our category systems through conscious acts of recategorization (though, through experience in the world, our categories are subject to unconscious reshaping and partial change). We do not, and cannot, have full conscious control over how we categorize. Even when we think we are forming new categories, our unconscious categories enter into our choice of possible conscious categories.

Most important, it is not just that our bodies and brains determine that we will categorize; they also determine what kinds of categories we will have and what their structures will be. Think of the properties of the human body that contribute to the peculiarities of our conceptual system. We have eyes and ears, arms and legs that work in certain very definite ways and not in others. We have a visual system, with topographic maps and orientation sensitive cells, that provide structures for our ability to conceptualize spatial relations. Our abilities to move in the ways we do and to track the motion of other things give motion a major role in our conceptual system. The fact that we have muscles and use them to apply force in certain ways leads to the structure of our system of causal concepts. What is important is not just that we have bodies and that thought is somehow embodied. What is important is that the peculiar nature of our bodies shapes our very possibilities fro conceptualization and categorization.