If you cannot solve the proposed problem do not let 
this failure afflict you too much but try to find consolation
with some easier success, try to solve first some related
problem; then you may find courage to attack your original
problem again. Do not forget that human superiority consists 
in going around an obstacle that cannot be overcome directly, 
in devising some suitable auxiliary problem when the original
one appears insoluble. Could you imagine a more accessible
related problem? You should now invent a related, not merely
 remember one; I hope that you have tried already the 
question: Do you know a related problem?
    The remaining question in that paragraph of the list
which starts with the title of the present article may have a 
common aim, the VARIATION OF THE PROBLEM. 
There are different means to attain this aim as GENERALISATION, 
SPECIALISATION, ANALOGY, and others which are various
ways of DECOMPOSING AND RECOMBINING.