This phrase has two meanings.

Those who like formal methods are talking about using mathematics and
logic to solve problems and develop software.  They tend to be quite agile
in the way they use one or more formal languages based on discrete
mathematics and symbolic logics.  The agility comes from the symbols,
and from experience in using them.   However some formal methods use
powerful tools.

On the other hand, others equate formal methods with: too much documentation,
high ceremony, and being told what to do.  They, therefore, don't like
formal methods.

''Hmm..then there is yet another (more intelligent) group out there who sees the advantages of '''both''' formal methods '''and''' pragmatic methods.. combining '''all''' aspects of testing,  formalizing, '''and''' specifying. Any formalist worth his salt should '''fill in some values''' and try their specs out. Every math teacher in the world that I knew (and every scientist), always tested his/her equations with experiments, pencil, and paper. See also TheBestOfBothWorlds, WinWin, and ViolentAgreement.''
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CategoryFormalMethods