Electromagnetism - Why electric and magnetic fields are manifestations of the same phenomenon Maxwell's equations reveal an interdependency between electric and magnetic fields, inasmuch as a time varying magnetic field generates a rotating electric field and vice versa. Furthermore, the equations predict that even in the absence of any sources one can have self propagating electric and magnetic fields, so called electromagnetic waves.
However, is it correct to say that although Maxwell's equations show that electric and magnetic fields are interdependent, they do not imply that the two are different aspects of the same underlying physical phenomenon?! 
Given this, is it then correct to say that it is not until one takes into account special relativity that it becomes clear that electricity and magnetism are different manifestations of the same underlying phenomenon?
Indeed, if one considers a frame of reference in which only an electric (or magnetic) field is observed, then, upon a Lorentz transformation to another frame of reference, it is found that one will observe a combination of electric and magnetic fields. This implies that the two are not independent of one another, since there is no observer independent manner in which one can separate electric and magnetic fields, hence implying that they are manifestations of the same underlying field - the electromagnetic field?! 

Edit
In essence, my question is, can one deduce purely from Maxwell's equations that the electric and magnetic fields are actually "the same" field, or is this (necessary) unification not explicitly confirmed until one takes into account special relativity?
 A: Electric and magnetic fields are field strengths of a gauge field. If you consider any matter field/particle Lagrangian, its coupling constant is the same for Electric and magnetic fields. 
For eg. classically in the Lorentz force equation $\vec{F}=q(\vec{E}+\vec{v}\times\vec{B})$. Notice that $q$ is the parameter that gives the coupling of the particle with Electric as well as magnetic field.
This is what we mean when we say the two forces are unified. 
Edit: Reply to whether historical approach is the one to use relativity
I have to disagree. Electric and magnetic field were realized to be the same once Maxwell wrote his equations and light was found out to be an electromagnetic wave by Hertz. It is true the Maxwell equations are Lorentz covariant and when you do that you have a single four potential that gives electric and magnetic fields. And then you add coupling with relativistic matter Lagrangians. Then it is natural to have a single coupling constant. So it was rather me who was taking the historical approach. Anyhow it is also modern. When you consider the standard model, weak interaction and electromagnetic interaction are given by the same $SU(2)_L$ field multiplet. But there are still two coupling constants which is why it is not a unification
