Principles Of Human Knowledge - pg. 60

Malebranche. There were various problems for Descartes, but among those that attracted most attention was the problem of interaction -- the question how mind and matter can influence each other if they are so different. We know (or think we know) that our bodies more because we will that they should, and that pain will occur if we cut ourselves with a knife. How is this possible? Malebranche saw this difficulty as related to a more general problem how physical things could be said to be causes. He argued that they could now. It was not just that they are inert -- the point that Berkeley makes much of. It was also that there was no coceivable necessary connection between one physical event and another; and for Malebranche there can be no causation without a necessary connection. There is, of course, a necessary connection between the will of God and changes in the world. So the only possible cause is God. As such a cause, God can act so as to move our bodies when we will to move, and to affect our minds when the world collides with us. He also acts to cause a physical event when suitable physical conditions occur. Within this picture the interaction problem fails to arise, since there is no difficulty at all in supposing God capable of affecting either minds or matter on suitable occasions.