Creation implies a dynamic process. That is Shakti. In the western world the term is nature. It is true that in itself Shakti explains everything.
The unsolved question would then be on what stable basis or ground of existence is this enormous dance taking place? The stable ground then provides the basis, the foundation, to steady the feet of Shakti else everything becomes too chaotic and falls apart. It is like the canvas on which the cosmic painting is taking place. Shiva provides the stable ground on which the dynamic dance of Kali (the power that drives Kala or Time) is taking place.
Affectionately,
Alok Da
