An important aspect of Leibniz's Monadology and Discourse on Metaphysics is his conception of simple substance and interaction. Leibniz attributes the term Monad to all simple substances. Monads are beings without parts, for which “neither extension, nor form, nor divisibility are possible” (M3). Monads can exist as determinate, necessary, finite, or infinite beings. For Leibniz, God exists as the one necessary and infinite Monad, who is solely responsible for the infinity of many determinate, independent, and finite Monads in the universe, all of which depend on God for their existence (D14). Leibniz asserted that all created Monads “possess within them a certain perfection; there is a kind of self-sufficiency that makes them the source of their own internal actions” (M18). But some simple substances are also endowed with distinct qualities of perception and accompanied by memory; these types of Monads are called Souls, and the example of which is the human mind (D12; M19). These finite Monads are considered independent, even though they depend on God, because each exists as a separate universe, which cannot interact with other finite Monads or with the outside world. Interaction, which is defined as a transposition of parts, or matter exchanged and arranged, cannot occur between the consciousness of the Monad and the external physical world, because minds do not have parts with which to interact with the extended and divisible parts of the body. Leibniz's conception of an infinity of simple substances and the denial of mind/body interaction was developed in response to Spinoza's assertion that there is only one substance and his idea of ​​parallelism , which states that thought and extension express the same medium. of paper ......uence another. Another problem that Leibniz creates concerns his idea of ​​the necessity of God. Leibniz argues that God is necessary, but if God is necessary, then it seems that any choice God makes to reveal these innate ideas to people must also be necessary, and therefore our actions must be necessary. It seems contradictory to claim that your actions are certain and determined by God, but that you are not necessarily obligated to carry them out. It would seem that God determines your actions because those actions are the best possible choice, and since God can only choose the best possible choice, it would seem that God does not have free will to make his decision, so all other actions possible would be they cannot even be designed by God because they are not possible choices, since they are not the best, and it is only possible for God to choose the best.