This enigmatic body would act as a kind of transducer (a system that can transform one type of energy into another) allowing the soul to convey the sensations of the outside world that have impacted the body, and also transmit orders to the body through the action momentum to the animal spirits that they, in turn, act on the muscles to Descartes, the human body operates on mechanical principles and is linked to the immaterial soul through the pineal gland (H). In the figure, she acts as a vehicle through the sense of vision. (The Treatise on Man, published in 1664, after his death.) A reaction against the Cartesian interactionism: For Malebranche the body and soul are two separate and unrelated entities. The series of brain and mental events run on parallel tracks, unaffected. It is only the will of God, present in every act, which performs the "miracle" to correlate both types of events so that at certain bodily events (eg., A stroke) occurring in certain mental events (eg., pain), or vice versa (body movement, the will to move) is why the doctrine is called "occasional", being omnipresent God's will on every occasion that the mental and physical appear correlated. Leibniz's preestablished harmony Like Malebranche, Leibniz understood that the mind and body do not interact per se and are related only by the will of God. The difference is that Leibniz believes that God, the beginning of time, synchronized series of mental and physical events such as two clocks.