Is using an heuristic to make a decision logically sound?

By its very definition it is logical - even if that logic may be abstract or incomplete.

Whether it is sound (logically) or not, is determined by what is called a validity test.

 

Here is a diagram based upon traditional logic. Looking these in a more detailed way:

With an heuristic, its ‘validity’ is solely determined by its usefulness to a purpose. The measure or nature of that usefulness is how effective it is.

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