The PF594 Agrument is one of the Pandora actions, turning the gun into a flying fortress, armed with multiple rocket lauchers. It depletes Disaster gauge.
Argument puts Dante in an armed hovering machine, that can shoot out homing rockets. It grants him a legitimate ability to fly. Although Argument requires the Disaster gauge to be used it can be activated with empty bar. However, you will be able to make only 1-2 shots and fly no more than a second.