 
 
 
Welcome to the UFBA Philosophy Lectures everyone. I am Emiliano Boccardi and this is the
first of a series of conversations with
the logician and philosopher Graham Priest.
Throughout the history of Western
thought, very few philosophers dared to
question the principle which says that
contradictions cannot be true. So
much so that hardly anyone after
Aristotle has tried to defend it.
Professor Priest belongs to the small
number of philosopher who did question
it, in good company of Heraclitus and
Hegel, among others. He thinks that some
contradictions are actually true and
he's going to tell us why. Let us welcome
Graham Priest. Welcome, Graham how are you?
Thank you very much for being with us.
Hi, Emiliano.
Thank you for your welcome, thank
to you and your readers. It's a
pleasure to be here.
I mean I'm locked down in the United States. I expect you're locked
down where, you are well is this yeah at
least those at the present juncture and
lockdown as well yeah strange times we
find ourselves in but you make the
business trip okay so for today I would
like you to introduce some of the basic
concepts that I needed to understand
your views about contradiction so could
you give us a rough and ready
characterization of the notion of
contradiction what is a contradiction
and of the principle of
non-contradiction in its canonical
formulations okay
so first of all a contradiction
maybe this is best explained by a few
examples so the sun is shining the Sun
is not shining suck trees and mortal
Socrates is not mortal all made immortal
some men are not mortal so these are
pairs of statements such that if one is
true the other is false so logician sort
of categorized various pairs of
statements as contrary as contradicts
our countries we don't need to go into
the details now but the sort of
characterization of a conflict repair is
one this one goes back to Aristotle such
that if one is true the other is false
and if one is false the other is true
that's a contradiction and can you tell
us what the principal said that there's
been several formulations of the
principle of non-contradiction XANA I
think after look as the average is
standard to distinguish a analogical
formulation from a logical formulation
and from a psychological formulation
could you give us a characterization of
the principle what you think is the best
way to characterize the principle sure
this is less easy than my mother thought
dolly thism the view that some
contradictions are true has now been a
debate this coding current philosophy
logic metaphysics for us but some 40 or
50 years and as you might guess it's got
kind of a tangled sometimes one of my
colleagues wrote a paper on what the law
of non-contradiction means and he
enumerated something like 12 and 30
different possible variations yes
there's not get into the scholarly
niceties too much the way that Aristotle
characterizes a lot of contradiction is
kind of simple no contrary could be true
that is probably a good starting place
there are problems with that because a
daily theist believes that some
contradictions are true and if you
believe that some contradictions are
true
you might also believe that local
contributions are true that's a
contradiction okay but if you're not
really out contradictions out of hand
then it's not obvious why you should
rule that one out
so that's sick kind of subtlety so if
you want to get around that problem
you've got a characterize the laws
slightly differently and it's got to be
something like you can't accept a
contradiction rationally so that shifts
the register of the principle it talks
about what you can account rational and
B accept but there's a first cut
Aristotle's characterization is pretty
good you know contradictions can't be
true due for the moment until we need to
look at a question more carefully
