Do philosophers really understand the concept of free will and have it formally

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Do philosophers really understand the concept of free will and have it formally defined? Dr. Maitzen in response to question 5711 was able to answer the question without asking what free will is yet for question 24592 he seemed not to know what free will is and seemed to treat is an abstract construction so is it just an abstract construction and if it is, why create the concept in the first place?