Have you seen it before? It is possible that we have 
solved before the same problem that we have to do now, 
or that we have heard of it, or that we had a very similar
problem. These are possibilities which we should not
fail to explore. We try to remember what happened.
Have you seen it before?  Or have you seen the same problem
in a slightly different form?  Even if the answer is 
negative such questions may start the mobilisation of 
useful knowledge.
     The question in the title of the present article is often
used in a more general meaning. In order to obtain the 
solution, we have to extract relevant elements from our
memory, we have to mobilise the pertinent parts of our
dormant knowledge (PROGRESS AND ACHIEVEMENT). We 
cannot know, of course, in advance which parts of our 
knowledge may be relevant; but there are certain pos-
possibilities which we should not fail to explore. Thus, any
feature of the present problem that played a role in he 
solution of some other problem may play again a role.
Therefor, if any feature of the present problem strikes
us as possibly important, we try to recognise it. What is
it? Is it familiar to you?  Have you seen it before?