To: Larry B.
From: Geoffrey Klempner
Subject: Xenophanes on the limits of human knowledge
Date: 13th June 2008 12:36

Dear Larry,

Thank you for your email of 4 June, with your second essay for the Ancient Philosophy program, in response to the question, 'What is it to 'know' that something is the case? Can the truth of a scientific theory ever be known? Illustrate your answer by reference to Xenophanes' reflections on the limits of human knowledge.'

It is clear from your answer that you have thought a lot about this question. In relation to your question about Pierce, one of the most important contributions that American thinkers have made to philosophy is through the pragmatist tradition: through the work of Pierce, Dewey, James. This has had an important impact on the philosophy of science and philosophy generally. The question of the relation between knowledge and action is crucial to this essay.

I liked the examples you gave of evidence based on fingerprints and DNA samples, as well as the broader question to what extent expert scientific testimony should be accepted as 'fact'. I'll begin with these because they illustrate an important aspect of the question of what attitude we should take to scientific claims in general.

Courts of law seek to convict 'beyond reasonable doubt'. This formula neatly captures the idea that there can be room, in an abstract or theoretical sense for doubt which is not reasonable. We have to distinguish between doubts that we can imagine theoretically, and doubts which are real and which need to be taken seriously, and are therefore 'reasonable'.

The criteria for 'reasonable doubt' in this sense are linked to action. If a chair looks a bit rickety, then it is reasonable to test it first before sitting on it. But a person who feels compelled to 'test' every chair he sits on would be considered neurotic. If a chair looks solid, if no-one has warned you about the chair, if the manufacturer hasn't done a recall, then it is not reasonable to doubt whether it will bear your weight.

With other things that human beings use, greater care needs to be taken because the potential consequences are worse than just a few bruises. Before take-off, a pilot goes through a set routine checking all the control surfaces etc. because any failure could lead to catastrophe.

What should we then say, when a man's life, or freedom, hangs in the balance? You suggest that one should always allow the 'possibility of parole'. As I understand this (correct me if I'm wrong) parole is granted on the understanding that the individual paroled was guilty but has served a sufficient length of time in jail: the punishment is sufficient for the crime, and that there is no danger to the public. Jail without the possibility of parole is only for the most serious crimes. Even in this case, however, there remains the possibility of appeal on the basis of new evidence.

One of the objections to capital punishment is that there is an absolute cut-off point -- the convicted man's execution -- beyond which he cannot be saved by any appeal. In reality, this has led in the US to extraordinary lengths of time spent on death row, as the prisoner makes one appeal after another. One of my Pathways students has spent over 20 years in San Quentin.

For a person who is convinced that capital punishment is justified for some crimes, there is a conflict here between the idea that judgement is for the sake of action -- the need to punish the guilty and protect society -- and the concern to avoid the execution of those innocent of any crime.

Contrast the case which you consider at the end of your essay, the evolution-creationism debate, where there is no urgent 'action' that a person needs to perform depending on whether they are an evolutionist or a creationist. There are many devoutly religious Christians who accept that the theory of evolution provides the 'best explanation', and see this as being to the greater glory of God. However, to say that no urgent action follows belief in one or other theory does not mean that the debate is without practical consequences. I would argue, as a firm defender of science, that the mental gymnastics required to maintain belief in creationism are a serious obstacle to the development of the abilities required for a scientific investigator.

Xenophanes made two main contributions to epistemology, and we have been considering one of them: the question of the status of scientific theories. I think that in your enthusiasm to pursue this question, you may have missed the main point of his claim about the Thracians and Ethiopians.

What Xenophanes is pointing to here is the possibility of an explanation for a person's beliefs which calls those beliefs into question, on the grounds that 'That's just what a person in your situation would believe.'

It is possible that God does have blue eyes and red hair. But the Thracians (on my reading of Xenophanes) never argued, 'God created us, therefore God looks like us, therefore God has blue eyes and red hair.' That would be a sort of rational justification for their belief, though not a very good one. (God made lots of things, cows, sheep, elephants: why doesn't God look like an elephant?) Rather, the Thracians have a predisposition to believe that God is like them because of an understandable prejudice.

Many of our beliefs are based on prejudice (I am using this in a neutral sense which does not necessarily imply any criticism). People hold a particular religious faith because their parents held it, not because they have looked at all the different religions and made a 'rational choice'. Some prejudices can and should be examined (racial prejudice, for example). But no-one has succeeded in examining all their prejudices, nor would this be possible.

In the field of forensic science, investigators are trained to gather the evidence without pre-judging what is important or unimportant because the tiniest fragment can hold the most important clue. Yet no-one would doubt the value of the detective's ability to form an accurate snap-judgement, not based on a 'rational evaluation of the evidence' -- which comes later -- but rather through intuition based on experience. 'This theft was the work of professionals', 'That man is lying', and so on.

All the best,

Geoffrey