ABSTRACT
It is a remarkable achievement of contemporary philosophy, at least since the publication of Wittgenstein's Philosophical Investigations, that it has rendered the concept of privacy highly problematic. In his Philosophical Investigations, Wittgenstein explores, questions, and casts aspersions on the notion of a self-taught language that others could not learn or understand, a language so private that it would have not only a private use but also a private semantics. Anthony Kenny has been an influential proponent of the view that Wittgenstein's later philosophy is an attack on what he calls Cartesian privacy. According to Kenny, Descartes' innovation in the philosophy of mind was the substitution of privacy for rationality as the mark of the mental. The private language charge against Descartes would have validity if Descartes had arrived at the Cogito by simply contrasting the certainty of his knowledge of his own thoughts and sensations with the uncertainty of his knowledge of other people's thoughts and sensations.
