Ideas are the great warriors of the world, and a war that has no idea behind it, is simply a brutality.

Garfield contrasts brute force with the motivating power of principles. “Ideas” here stand for moral, political, or philosophical commitments that can justify sacrifice and discipline collective action. By calling ideas “warriors,” he suggests that the deepest battles are fought in the realm of belief—over what a society values and what ends it pursues. The second clause is a warning: when violence is detached from any coherent ideal or ethical purpose, it degenerates into mere cruelty. The quotation is often invoked to argue that legitimate conflict requires a defensible cause and that power without guiding principles becomes barbarism.