Often things are considered in only one light. Something is entirely good or bad. This is often a function of advocacy, human nature, or whatever, but TwoThingsCanBothBeTrue.

Mozilla is a failure because it took many years to write and allowed IE to take over the browser market. Mozilla is a success because 
it is a good product. Both can be true.

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It might also be true that Mozilla is a success because it took many years to write and allowed the inclusion of current technologies, which made it a good product. 

It might also be true that Mozilla is a good product because it does what you want it to do, on the machine you are presently using.

ItDepends on your choice of success criteria! 

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Look into FuzzyLogic, which provides a much better explanation of this than trying to use Boolean logic.

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See FalseDichotomy