This is a classic work of analytic philosophy. Moore draws a number of distinctions, and is attempting to be extremely careful and precise. Reading his article requires a great deal of concentration. Read slowly, reread paragraphs that aren't clear the first or second time, and take notes. The following questions and comments may help you understand the essay.

• Comment: Moore begins by discussing the philosopher Immanuel Kant (late 1700s), who took up the problem of whether we can prove the existence of 'things outside of us' (70). Kant made a distinction between 'things in themselves'(which are transcendentally external) and things as they appear to us (which are empirically external) (70), and believed we can't prove the existence of things as they are in themselves.

Moore takes up this problem of whether we can prove the existence of things. He thinks we can. But before doing this, he spends a great deal of time trying to be very clear about precisely what sort of things he is talking about. So he distinguishes all sorts of possible 'things' (physical bodies, shadows, reflections in mirrors, after-images, pain in humans, pain in animals, soap bubbles, etc.).
 
• Moore begins by distinguishing external things, things external to our minds, and things external to us (70). How are these different?

 
• Moore makes a crucial distinction between things which are to be met with in space, and things that are presented in space.
• He gives several examples of things that are presented in space but that are not met with in space (71 ff.). What are they?
• Things met with in space include physical objects. Do they include shadows?
• Not all things met with in space are presented in space (74). What are examples?
• How would you classify a reflection in a mirror? (75)

 
• The things that are presented in space but which are not met with in space can be described, says Moore, as 'things-in-our-mind' as opposed to things external to our minds. (77-78). How do we know that the things external to our minds are really external and not just 'in our mind'? In addressing this question, Moore clarifies what we mean in saying that some things are 'in my mind' and some things are external to my mind (79 ff).
• How does he draw the distinction? In other words, what is his criteria for saying that a thing is external to our (human) minds and not just in our mind?
• On p. 80, Moore notes that when animals feel pains or see after-images, these are external to our (human) minds, but are not met with in space. So he concludes that not all things external to our minds are met with in space. Why do you think he bothers noting this?
• In explaining the above distinction, Moore discusses soap bubbles (80). How does his discussion of soap bubbles help him make his point?
 
• Comment: Moore says that he can prove the existence of an external world so long as he can prove that there exists a particular thing: if he proves a sheet of paper, or a human hand, exists, then he can prove the existence of an external world (81). Now Moore has spent his whole article so far distinguishing different sorts of things: things presented in space, things met with in space, things external to our minds, things in our minds, external things, physical things, shadows, soap bubbles, after-images, pain, etc. etc. He doesn't think that he can prove the existence of an after-image in a horse, which is a thing external to Moore's (and every human's) mind; but he does think he can prove the existence of a thing met with in space.
 
• Moore then proves the existence of a thing-his hands-in a single, short paragraph. He says his proof is perfectly rigorous (81). What is his proof?
 
• Moore notes that not every philosopher will be satisfied with his proof. He notes that some will want him to prove the key premiss of his proof, but he says he can't.
• Can you imagine how to prove this premiss?
• Moore insists that even though he can't prove his key premiss, he has given a conclusive proof (84). Do you agree?
• Moore refers to Descartes on p. 84. Descartes asked, how can we be sure that what we believe we see isn't an illusion or a dream placed in us by a great deceiver? What is Moore's response to Descartes, and does it satisfy you?