Some observations about usage of the concept of knowledge, which have a bearing on the arguments presented here.
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The virtues of rigour its connection with scepticism.
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Some arguments against the possibility of Knowledge, and the substantive content of those arguments.
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Knowing how and knowing that
We are here concerned primarily with knowledge of the truth of propositions, rather than with other kinds of knowledge such
as that of some skill.
The following discussion should be understood to concern only that (rather broad) special case.
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What is Knowledge?
The usage of the word "know" is diverse and inconsistent.
To know a proposition, it often seems, one must have conclusive grounds for believing it to be true.
Even in the absence of grounds for reasonable doubt in the truth of the proposition may not be sufficient
if the grounds for its affirmation are subject to any doubt whatsoever.
hBy contrast, in some contexts it suffices to be in possession of certain information to be said to know, without consideration
of the strength of the grounds, provided only that those grounds are sufficient to induce belief.
In the discussion which follows here, it is that former sense, which is mainly at stake, for this seems to be the sense in
which radical sceptics consider knowledge.
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Doing Without Knowledge
Difficulties with the word "know" are not dissimilar to those with the concepts "hot" and "cold", whose significance is equally
fluid, context sensitive, or uncertain.
For scientific purposes, the concepts "hot" and "cold" are displaced by numerical measures of temperature.
Though it may be very important whether something is hot or cold, it is not important that those worlds be used in describing
it.
For many purposes that terminology can be discarded.
Similar considerations apply to the concept of knowledge.
Instead of the binary consideration "Do we know proposition p or not?" we may in some contexts prefer the consideration "What
confidence can we have in the truth of p?", more so perhaps if the concept "confidence" here can be made precise.
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The value of Knowledge
Much (if not all) knowledge has some utility.
Some kinds of knowledge allow us to predict what the conseqences of some of our
actions or possible actions.
This permits choice betweem actions based on the desirability or otherwise of their consequences.
If some of our beliefs are incorrect, then we risk mistaking the consquences of some of our possible actions, and coming to
incorrect conclusions about what course of action is optimal and suffering less desirable outcomes.
For this reason it is desirable putative knowledge be rigourously tested in some way with a view to discarding any supposed
knowledge which might be incorrect.
This we might describe as exercising a prudent skepticism.
Though I have phrased the above considerations as if we were considering science and engineering, to most people
it is less exalted kinds of knowledge which prudence dictates be treated with scepticism.
Thus, when approaching an election, a degree of scepticism about the claims and promises made by politicians may be prudent,
for even the most honest politicians may be mistaken in crucial matters, and the rest will be even more likely to mislead
us.
Perhaps of even greater personal significance, the claims made or implied about financial products or assets are important
to us in chosing
how to invest our savings, but may not be correct.
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Preliminaries
The arguments put forward by the academic and Phyrrhonean sceptics were extensive and varied.
Rather than a presentation of those arguments, I put forward some very general arguments which
are helpful in explaining the aspects of scepticism which we carry forward.
A case against the possibility of knowledge can be made in the following way.
First we take knowledge to involve absolute certainty (conferred by absolutely conclusive justification),
and then we argue that no such thing is to be had.
The latter part comes in two stages.
First we suppose that deductive reason yields certain truth.
Then we argue that reasoning to empirical truths fails of that standard,
Then we turn to scepticism concerning logical entailment.
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Regress of Justification
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