  We discuss the freedom in the background field (vacuum) on top of which the
solitons are built. If the Hirota bilinear form of a soliton equation is given
by $A(D_{\vec x})\bd GF=0,\, B(D_{\vec x})(\bd FF - \bd GG)=0$ where both $A$
and $B$ are even polynomials in their variables, then there can be a continuum
of vacua, parametrized by a vacuum angle $\phi$. The ramifications of this
freedom on the construction of one- and two-soliton solutions are discussed. We
find, e.g., that once the angle $\phi$ is fixed and we choose $u=\arctan G/F$
as the physical quantity, then there are four different solitons (or kinks)
connecting the vacuum angles $\pm\phi$, $\pm\phi\pm\Pi2$ (defined modulo
$\pi$). The most interesting result is the existence of a ``ghost'' soliton; it
goes over to the vacuum in isolation, but interacts with ``normal'' solitons by
giving them a finite phase shift.
