  It is argued that a dual symmetry is needed to naturally explain experimental
limits on color confinement. Since color is an exact symmetry the only
possibility is that this symmetry be a dual symmetry, related to non trivial
spatial homotopy. The sphere at infinity of 3-dimensional space being
2-dimensional, the relevant homotopy is $\Pi_2$, the corresponding
configurations monopoles, and the mechanism dual superconductivity. The
consistency of the order-disorder nature of the deconfining transition is
compared with lattice data . It is also shown that the only dual quantum number
is magnetic charge and the key quantity is 't Hooft tensor, independent of the
gauge group. The general form of the 't Hooft tensor is computed.
