Week 2: Moore, Proof of an External World

DQ-1. Consider Moore's 'Here is One Hand' argument:

Moore's (1939) 'Here is one hand' Argument

  1. Here is one hand (holding one hand up), and here is another (holding the other up).
  2. If here is one hand, and here is another, then two human hands can be met with in space.
  3. If two human hands can be met with in space, then things in the external world exist.
  4. Therefore, things in the external world exist.

Evaluate this argument from the perspective of Moore's second adequacy condition for a good argument. Namely, "Known premises: the premises have to be true, and known to be true." Are they? Comment on each in turn.


DQ-2. Assume the following sentence is true for each of the subquestions below: "If I might be dreaming, then I do not know that there are two hands."

(a) Suppose you also assume the following sentence: "I might be dreaming." What can the sceptic conclude from this via a valid argument? Explain.

(b) Suppose instead that you assume the following sentence: "I know that there are two hands." What can Moore conclude from this via a valid argument? Explain.

(c) Are either of these two arguments more reasonable than the other one? Why or why not? Discuss the implications for Moore's 'Here is One Hand' argument.


DQ-3. (Optional) Discuss Carnap's 'empiricist response' to the sentence, "Things in the external world exist": under what conditions would Carnap take such a sentence to be meaningful? Does the sentence satisfy this criterion of meaning?