A surgical cutting and fastening instrument comprising: an end effector comprising a moveable cutting instrument for cutting an object positioned in the end effector; a main drive shaft assembly (48, 50, 52a-c) connected to the end effector; and a handle connected to the main drive shaft assembly, wherein the handle comprises: a gear drive train connected to the main drive shaft assembly; characterised by a motor for actuating the gear drive train; and a firing trigger for actuating the motor and connected to the gear drive train such that the loading force on the firing trigger is related to the loading force experienced by the cutting instrument in the end effector, wherein the surgical cutting and fastening instrument further comprises: a run motor sensor for sensing retracting of the firing trigger, wherein, when retraction of the firing trigger is sensed by the run motor sensor, the motor is signaled to forward rotate to cause cutting of the object positioned in the end effector by the cutting instrument; a reverse motor sensor for sensing an end of a cutting stroke of the cutting instrument such that when the reverse motor sensor senses the end of the cutting stroke, the motor is signaled to reverse rotate to retract the cutting instrument; and a stop motor sensor for sensing retraction of the cutting instrument such that when the stop motor sensor senses retraction of the cutting instrument, the motor is signaled to stop rotating. an end effector comprising a moveable cutting instrument for cutting an object positioned in the end effector; a main drive shaft assembly (48, 50, 52a-c) connected to the end effector; and a handle connected to the main drive shaft assembly, wherein the handle comprises: a gear drive train connected to the main drive shaft assembly; characterised by a motor for actuating the gear drive train; and a firing trigger for actuating the motor and connected to the gear drive train such that the loading force on the firing trigger is related to the loading force experienced by the cutting instrument in the end effector, wherein the surgical cutting and fastening instrument further comprises: a run motor sensor for sensing retracting of the firing trigger, wherein, when retraction of the firing trigger is sensed by the run motor sensor, the motor is signaled to forward rotate to cause cutting of the object positioned in the end effector by the cutting instrument; a reverse motor sensor for sensing an end of a cutting stroke of the cutting instrument such that when the reverse motor sensor senses the end of the cutting stroke, the motor is signaled to reverse rotate to retract the cutting instrument; and a stop motor sensor for sensing retraction of the cutting instrument such that when the stop motor sensor senses retraction of the cutting instrument, the motor is signaled to stop rotating. a run motor sensor for sensing retracting of the firing trigger, wherein, when retraction of the firing trigger is sensed by the run motor sensor, the motor is signaled to forward rotate to cause cutting of the object positioned in the end effector by the cutting instrument; a reverse motor sensor for sensing an end of a cutting stroke of the cutting instrument such that when the reverse motor sensor senses the end of the cutting stroke, the motor is signaled to reverse rotate to retract the cutting instrument; and a stop motor sensor for sensing retraction of the cutting instrument such that when the stop motor sensor senses retraction of the cutting instrument, the motor is signaled to stop rotating.