Although the real numbers form an extremely useful number system, the decision to interpret the notation "0.999..." as naming a real number is ultimately a convention, and Timothy Gowers argues in Mathematics: A Very Short Introduction that the resulting identity 0.999... = 1 is a convention as well: However, it is by no means an arbitrary convention, because not adopting it forces one either to invent strange new objects or to abandon some of the familiar rules of arithmetic.
Walaupun sistem bilangan real membentuk sebuah sistem bilangan yang sangat berguna, keputusan untuk menginterpretasikan frasa "0,999…" sebagai penamaan sebuah bilangan real pada akhirnya merupakan sebuah konvensi, dan Timothy Gowers berargumen dalam Mathematics: A Very Short Introduction bahwa identitas 0,999… = 1 itu sendiri juga merupakan sebuah konvensi: However, it is by no means an arbitrary convention, because not adopting it forces one either to invent strange new objects or to abandon some of the familiar rules of arithmetic.