Solipsism Exposé Addendum
So, what about reasoning then? Useless posturing? No, of course not. It's not to abandon reasoning, or throw hands in the air in futility, rather the opposite. It's to recognize the difficulties involved in knowledge acquisition; something students of history (of science and philosophy in particular) should know all too well. Common sense, heuristics, careful inductive and abductive reasoning are indispensable for anyone wishing to learn, and that's the natural
modus operandi of most healthy individuals in any case. (Outside of philosophy, solipsism is largely pathological, reported by doctors and asylums.)
Numerous philosophical branches have been charged with solipsism, including, but not limited to, Cartesian skepticism (obviously), (pure) phenomenology, subjective idealism (and some other idealisms), postmodernism (when applied in metaphysics). It crops up in numerous places, and is occasionally used argumentatively to deny just about anything, i.e. a rhetorical tactic.
But, in the requisite Wittgensteinian tradition, languages sure help. Regardless of whether or not there are private languages, public languages enable sharing of experiences.
