To all who disagree with my statement that there is an independent document (or notion) that specifies requirements and program != specification, how do you def

To all who disagree with my statement that there is an independent document (or notion) that specifies requirements and program != specification, how do you define a bug? I say that a bug is where a program violates a requirement. If you say there is no independent source of requirements than the code, then I don't see what can be bug as the program is self-consistent.