An initial value problem is then a differential equation (ordinary or partial, or
even a system) which, besides of stating the
relation among the
derivatives, also, by giving the
initial conditions, specifies the values of the unknowns at some
point.
This makes it possible to get a unique solution from the infinite
number of potential ones. However, it should be noted that not all
possible choices of initial conditions specify a unique solution. It is
also possible that there will be more than one solution satisfying a
particular choice of initial conditions, or perhaps no solution. In
fact, one of the
main problems in the
theory
of differential equations is to determine what sort of initial
conditions will single out a unique solution of a given differential
equation.