I am reading Alfred Mann's translation of "Gradus ad Parnassum" and found a footnote that says that Fux considers a fourth that comes from harmonic division the of the octave (fifth-fourth) a consonance and a fourth that comes from arithmetic division of the octave (fourth-fifth) a dissonance.
What about fourths in multi-part writing that do not have either of the notes of the fourth in the bass? For example, third-fourth? What does Fux or other theorists have to say about this case?
Also, is this the reason why in classical harmony triads in root position and first inversion are used quite freely while triads in second inversion are a special case?