At the risk of digging old thread, I’ll try to refer back to original question.
I’ve been thinking about the essence of “testing” and I think that the core is really “seeking answers for questions”.
Sometimes questions are asked explicitly, sometimes we must state them ourselves. Sometimes we must provide thorough answer supported by various data (and we must prove that our support arguments are correct as well!), sometimes quick chat is alright. Sometimes it takes us weeks to find answer, sometimes we have them in matter of minutes. Sometimes we must provide answer to questions that are meant, not merely asked. Sometimes we must explain why our answer is sufficient. Sometimes we must work with clients to help them understand consequences of their questions, effort required to answer their questions and to help them refine their questions. And sometimes we fail to find answer we were looking for.
Yes, such definition is not specific enough. Many other professionals seek answers as well - scientists immediately spring to mind - and yet, they are not testers. There are many questions that testers have no interest in answering. We work within - broadly defined - IT, which limits scope of our work in some way. And finally, there probably should be something about how our work impacts other people and products we test.
Sometimes I feel that if we want to know “real truth” about testing, all substantial definitions are deemed to fail and should be abandoned. If we “really” want to understand what testing means, we must define it through usage of the word in the community of word-users and recognize that it changes and shifts meaning, it is elusive and sometimes self-contradictory. But then - such definitions, even if they are charming for some, aren’t really helpful.