In a way it is a combination of both. I see the root of all love in friendship first, for once the physical side of love begins to dwindle, there must be something which pulls people together. True friendship cannot exist without some form of love, be it platonic or otherwise. The desire for another person's well-being above your own, is the ultimate form of love, one that does not leave based upon dispute. It is part of the inner soul of the person, and should someone try to remove it, it would be like trying to remove the core of who they are. When that love is mutual, there is such a power and beauty that it shakes the world. If everyone could have that type of love for each other, there would be no wars or destruction. Unfortunately, most do not know what that type of love is, and thus we perpetuate ills against each other.
