Although there are several voices that shine the brightest as philosophers of philosophical skepticism, it is a topic which has captured the attention of a huge number of philosophers throughout time. The so-called challenge of radical skepticism has been raised and allegedly met time and time again. One of the aforementioned notable voices in the past century was G.E. Moore, who advocated what he and others have termed a ‘common sense’ response to radical skepticism (where radical skepticism refers to the position that knowledge—or certainly knowledge of the external world—is impossible).
Formally, Moore’s response proceeds from what is now in certain contexts called a Moorean shift—changing a modus ponens argument’s second premise to create a modus tollens argument which has an opposing conclusion (explained at more length below)—to support what is now in certain contexts called a Moorean fact (a notion that is more intuitively knowable to a person than philosophical premises that contradict the notion). That naming scheme ought to tell you how influential these ideas have been. G.E. Moore was a capable and perceptive philosopher, and his work on skepticism was inspirational for Ludwig Wittgenstein (who later tried to formulate a more rigorous account of Moore’s approach in notes which were assembled into a book after Wittgenstein’s death). Now I will point out why G.E. Moore’s confident argument is insufficient for meeting the challenge of radical skepticism.
Intuition All Alone: