override message for validations

Hi all,

Is it possible to override the default rails messages (:message => )
for validations
(validates_presence_of :first_name, :last_name, :email, :message =>
"you moron!") application wide without changing the rails code itself.

I need to translate it but want to avoid putting the translation next
to each validates_*

I prefer not to do to change rails code since I feel it hardens
upgrading.

Regards,
Stijn