A surgical system includes a robot with both an active mode and an inactive mode of operation, and a holding arm for holding a surgical tool, and an immediate deactivator for determining when a human operator manually manipulates a holding arm or a surgical tool depending on signals from at least one condition sensor. Immediately upon that determination, the immediate deactivator deactivates the robot. The holding arm includes a stiffener/destiffener for increasing or decreasing the flexibility of the holding arm. The stiffness of the holding arm can be sufficiently decreased in the inactive mode to allow a human operator to skillfully control repositioning the surgical tool into a new position while the flexible holding arm is connected between the robot and the surgical tool. Also, the stiffness of the holding arm can be sufficiently increased, for essentially locking it into a rigid fixed shape for providing sufficient rigidity in the active mode for the robot to reposition the rigid holding arm for repositioning the surgical tool to perform preprogrammed tasks initiated by surgeon command inputs. The holding arm is completely inactive in both the active and inactive modes of the robot.
