I'll let Justice Harlan's words explain:
"[T]he full scope of the liberty guaranteed by the Due Process Clause `cannot be found in or limited by the precise terms of the specific guarantees elsewhere provided in the Constitution.
This `liberty´ is not a series of isolated points pricked out in terms of the taking of property;
the freedom of speech, press, and religion;
the right to keep and bear arms;
the freedom from unreasonable searches and seizures; and so on.
It is a rational continuum which, broadly speaking, includes a freedom from all substantial arbitrary impositions and purposeless restraints, . . .