Leibniz's principle and psycho-neural identity

Can the Leibnizian principle of the indiscernibility of identicals be used as an argument against the psych-neural type identity, that is, against the theory according to which mental propertiens are nothing but neural properties? We argue that (1) Leibniz's law cannot provide a reason to reject the identity theory and (2) it makes very hard to distinguish between two different versions of the psycho-neural identity theory, the weaker 'token identity' theory and the stronger 'type identity' theory.