...The nature of jihad is of course one of the central questions of the conflict. Frequently I have had students from Muslim countries explain very passionately that our understanding of jihad is flawed. That what we think of as jihad — violent struggle to extend the domain of Islam — is actually the “lesser jihad.” True jihad is a moral struggle within each person to enjoin the good and resist evil, what is called the “greater jihad.” Some say further that the idea that force can be used to convert is not Islamic; it would make the greater jihad impossible because the convert would not sincerely believe. All this may be true, in their understanding of the faith, and I have no quarrel with it. Would that everyone felt that way.

Nevertheless, not all Muslims are as interested in this spiritual quest, and some of the more radical adherents of the faith are convinced that nonviolence is not an option. Andrew Bostom’s book shows comprehensively the historical roots of this school of thought, and its continuity over the centuries to the present day. It helps one understand jihad operationally; its use, its claims to legitimacy, its perceived inevitability. Whether this is or is not the way most Muslims view the concept of jihad in its totality is not particularly relevant because people sincerely engaged in “greater jihad” are not a national-security threat. Likewise, those terrorists who have made “lesser jihad” their avocation have no use for fellow Muslims who are seeking only to bring themselves closer to God’s ideal as they understand it. As the Ayatollah Khomeini said of those who argued that Islam was a religion of peace that prevents men from waging war, “I spit upon those foolish souls who make such a claim.”...