Guest Frank and M. Ted,
I believe you are both right with the respective approaches. But you have to have a basis of reference in order to "compose" or "improvise" a solo, regardless of whether that basis is studied, with all the pertinent semantics understood or, self taught. Scales ARE an integral part of that basis, as are other elements of music theory as well.

The end result is more or less the same, depending on the simplicity or complexity of the knowledge gained.