# [isabelle] checking if a formula is intuitionistically valid

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Hello,
I am sincerely interested in using isabelle but I meet real
difficulties in starting alone with it.
First of all, I would be happy if I'd succeed to use isabelle just as
as simple theorems checker for formulas of first order logic. For
example, I do not even succeed in checking the validity of a classical
formula like:
(p \to q) \leftrightarrow (\neg q \to \neg p) (1)
I know that it is not useful to get isabelle in order to use it at this
low level, but I would be happy to get help just with the syntax. I do
not know why when I try to read the manuals I meet always message of
error. Thanks to tell me how to translate (1) in isar. That will help
me.
The second question that I want to ask here is maybe very naive, but I
do not feel shame. Is it possible to use isabelle just to check it a
propositional formula is intuionistically valid, or just classically
valid? For example: can isabelle tell me that (p \lor \neg p) is not
(intuitionistically) valid? And what about first order intuitionist
predicate calculus?
Thanks for your help,
Jo.
- --
Joseph Vidal-Rosset
Université de Nancy 2
Département de philosophie
Bd Albert 1er
F-54000 Nancy
page web: http://jvrosset.free.fr
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