Private modifier not allowed within Interface

hello,
Can someone explain to me the logic behind not being able to declare a method's modifier as "private" when defining my Interface? When I do so the compiler generates the following error:
"modifer private not allowed here at line 23, column 16"
I change it back to public and its fine. One would think that the compiler would allow one to declare a method private within an Interface so long as the Implementation matches? Thanks in advanced.

The idea behind interfaces is to provide information to the outside world about a class that implements the interface. Specifically, it lets the outside world know about certain methods that can be called on instances of that class. That way, a class can use instances of any class that implements a given interface rather than commiting itself to one specific implementation only.
Since the outside world cannot see private methods, it doesn't make sense for interfaces to prescribe private methods in the first place. In fact, how a class deals with implementing a method is none of the interface's business...

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