The concept of "just war," which President Obama invoked in his speech in Oslo after accepting his Nobel Peace Prize, is the Christian equivalent of Islamic "jihad."
Conceptualized by philosophers like St. Augustine and St. Thomas Aquinas, the "just war" theory essentially seeks to reconcile Jesus Christ's turn-the-other-cheek principle with the secular need of nations to wage war.
It has been the fig leaf for Western wars for nearly 2,000 years.
The crucial difference between the Christian and Islamic versions of jus ad bellum is that in the latter even individuals are allowed to wage jihad, whereas in the former, the state has the monopoly on violence.
But then, the state, which German philosopher Georg Wilhelm Friedrich Hegel called "the march of God on earth," is a very Western concept, while political Islam is organized primarily along tribal lines.
That accounts for Islam's inability to modernize its political realm in terms of separating the temporal and spiritual components.
And that is the reason why individual and group violence is seen by the West as illegal and immoral, whereas the Islamic world regards it as a religious obligation.
Therefore, Obama's rationale for the Afghan war will remain incomprehensible to Islamists, and the modernized Christian world will continue to view jihadists as terrorists.