Newton, the sensorium of God, and the cause of gravity

It is argued that the sensorium of God was introduced into the Quaestiones added to the end of Newton's Optice (1706) as a way of answering objections that Newton had failed to provide a causal account of gravity in the Principia. The discussion of God's sensorium indicated that gravity must be caused by God's will. Newton did not leave it there, however, but went on to show how God's will created active principles as secondary causes of gravity. There was nothing unusual in assuming that God, acting as the First Cause, operated in nature by means of secondary causes; but it was unusual to devote as much time to discussing God's precise role as to discussing the secondary causes themselves. It is contended that Newton felt the need to do this to persuade readers that what might seem like a second cause that could not possibly work could be made to work by the omnipotent God.