Sun Tzu isn’t talking about deception as a cause or a necessary condition of war. He’s talking about deception as a tactic of war. The quote goes on to say: “Hence, when able to attack, we must seem unable; when using our forces, we must seem inactive; when we are near, we must make the enemy believe we are far away; when far away, we must make him believe we are near. Hold out baits to entice the enemy. Feign disorder, and crush him.”