I am reading Ousterhout’s A Philosophy of Software Design. In Section 2.3, Outserhout writes:

The signature of a method creates a dependency between the implementation of that method and the code that invokes it: if a new parameter is added to a method, all of the invocations of that method must be modified to specify that parameter.

Does a method really create a dependency between the calling code and its implementation?

I see how the calling code becomes dependent on the signature, but surely the implementation is arbitrary; it could be unimplemented (ignoring the parameters entirely), and therefore not dependent on the signature at all.

Perhaps the author meant that the dependency exists spacially between the calling code and the implementation? I could agree with this, but I suspect the truth of this idea depends largely (perhaps entirely) on your personal model of how these ideas fit together.