Mark Passio has a great, common sense definition of "violence" that I think everyone should adopt, because it makes things much more linguistically clear. To commit violence is to "violate" someone's natural rights. That is, the person who initiates force is violating the victim's right to go about unmolested. If the victim then uses force to defend themselves, they are not violating anyone, therefore, they are NOT using viol-ence. Self defense and violence are polar opposite versions of Force, with initiation as the distinction. In summary, you cannot use violence in self defense, because you are not the one violating anyone.