The way of Ninjutsu, when correctly practiced, is the Art of Protection Against Danger. The weapons in your arsenal become foresight, situational awareness, sensory acuity, and a honed intuition. These are the weapons which Gracian developed, advocated, and utilized in Spain against the brightest political and religious thinkers.

Prudence, discretion, circumspection, sagacity, discipline, and all the other attributes and qualities that Gracian encourages his reader to demonstrate are the selfsame attributes and qualities required of the shinobi. How, then, could Gracian's writings not be relevant to the contemporary practitioner of Ninjutsu?