> Hi, > > I was reading the category theory book by david spivak (I am new to > category theory) and I am not clear why the aspect > > [a book] has as author [a person] would not be valid, while > > [a book] has as first author [a person] is valid. > > The 1st is said to not be functional. It looks fine to me. Why is it > not functional? What is the difference? What does he mean by it is > 'not functional'?
He thinks that the authors of a book with more than one author are different persons.
He also thinks that a book always has at least one author who is also a person, and it is always clear who is the first among the authors who are also persons.
There must be one and only one if the relationship is to be functional in the sense he means it.