Leslie: I' ll show you that your quest for the treasure is irrational  Suppose you found a tablet inscribed, Whoever touches this tablet will lose a hand, yet will possess the world   Would you touch it  Erich: Certainly not  Leslie: Just as I expected  It is clear from your answer that your hands are more important to you than possessing the world  But your entire body is necessarily more important to you than your hands  Yet you are ruining your health and harming your body in your quest for a treasure that is much less valuable than the whole world
I rest my case
Erich is engaging in irrational behavior by pursuing his quest for the treasure.