Hi John,

 Bruno,Hi,
thanks for your speedy and considerate answer. Your
examples are so simplistic, as only the science of
logic can provide. Let me try better examples:

--- Bruno Marchal <[EMAIL PROTECTED]> wrote:

" For example you can know that "1+1 = 3" is false,
but
in that case you know the *truth* of the proposition
" "1+1=3" is false".

Could we figure anything beyond 101 elementary school
arithmetics?


Why? The point is just to agree (or agree that we disagree) on some definition. The point is that nobody can know "something false", as opposed to knowing that some proposition is false. It is better to illustrate such nuance with elementary propositions nobody (really) doubt about (of the kind 1+1 = 2, or "1+1 = 3" is false).




E.g.: People and scientists, priests, etc. KNEW for
many centuries, including the early medieval ages that
the Earth is the center of the world and everything
rotates around it.


They knew that? Or they believed that ? I don't think it makes sense to say they knew that, unless you have another definition of knowledge. It is up to you to explain the difference between belief and knowledge. Epistemologist generally agree that knowledge verify the

Bp -> p

formula (If I know p then p is true). This is just because the truth is put in the knowledge by definition. If not, it means we talk on beliefs. Of course many people pretend that they know some proposition, and occasionally they are wrong: but then they say (if honest): "ok I was wrong but I believed it", they does not say "ok I was wrong but I knew it". And I do think our definition should be coherent with the way we talk, unless there is a big reason to depart from the traditional use.




Then came Copernicus and said: this
is wrong, the sun is the middlepoint. And people
though reluctantly, believed it. Then came
cosmologists and said that is wrong, there is NO
center, everything - including the Sun is moving
around. And people believed it finally, in droves.
Until Eistein came around and procalimed: nothing
moves around anything, because all movement is
relative to the others, ---
ACCORDINGLY:
the notion that everything rotates around the Earth is
just as true as any other belief put forward ever
since. (Warum habe wir die Kröten gefressen?)


But this oscillation is a quite complex things, and the usage of the word "knowing" here is quite sophisticated (that is why I did limit myself to very elementary arithmetic exemple). All what I can say is that if the earh is at the center of the world then the priest knew it, and poor of us, we believe (wrongly) the contrary. If the earth is not at the center of the world then the priests did believed (wrongly) that, and we know better. But your example includes a notion of relativity which limits its use for making clear the difference between the notion of belief and knowledge.




Popper had the idea that
nothing in science can be proven as true, only
falsification is possible, does that mean that all
science is false?


It just means that all (empirical) science is uncertain.
Actually a large part of analytical science is also uncertain but for different reasons (and then with comp it can be shown that there are relations between those different sort of uncertainties), but it would be senseless to mention them before we agree on the basic vocabulary.


Bruno


http://iridia.ulb.ac.be/~marchal/


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