Correction

In an earlier post I said the following:

Clues are the characteristics of structures but we do not gather all the characteristics first and then rebuild the structure. We do not ask, what are the characteristics of this crime? Then, after finding all of them, start to reconstruct the crime. Following clues is a narrowing-down process; we look for clues as we go along, to help us narrow down.

What I have written above is not quite correct. Following clues is not always a narrowing-down process. Whether it is or not depends on the structures we are trying to reconstruct and the number and kinds of clues available. For example, suppose all parts of a straight line have faded away through the ravages of time except for two faint points. Do we need to go through a narrowing-down process to reconstruct the original line? No; all we need do is draw a line through those two points: the line drawn will correspond to the original line.

In crime detection, situations detectives face can sometimes come close to our example: all the clues needed are there and they are so obvious that it is easy to reconstruct what happened--no need to go through any narrowing-down process. They even have a term for it; they call a crime like this an open-and-shut case. (We have to be careful, however; sometimes an open-and-shut case could turn out to be more complicated than originally thought.)

In playing Sherlock Holmes sometimes we have to go through narrowing-down processes, sometimes we do not. Some investigations are complex; some, simple or simpler.

From our line example above we see also that sometimes all the clues we need can be collected first, before we carry out the reconstruction.