Such full understand is beyond the grasp of our finite minds, but is not beyond the grasp of God
Any object in the universe is connected in some way or another. Every substance is like an entire world and like a mirror of God, or indeed of the whole world which it portrays, each one in its own fashion. Each substance reflects all the others. No substance can really cause any change in any other. What happens to be causal interaction among substances is really a "pre-established harmony" among them, reflecting the fact that God created each one with an eye to all the rest.
The identity of indiscernibles - of all the harmoniously evolving substances in the universe, no two are alike in every respect. If any two were completely alike, they would be one substance rather than two.
The mere possibility of these other worlds defeats the implication that whatever happens in our world is necessary. Leibniz's view rule out human freedom. God has decreed that "the will shall always seek the apparent good in certain particular respects. He, without at all necessitating our choice, determines it by that which appears most desirable". Whatever we do stems from our own will, and is done in pursuit of our vision of the good. Hence, anything we do is our own responsibility. God inclines our soul without necessitating them.
Leibniz was dissatisfied with the way Descartes and Spin...
To say, as Descartes did, that there are two independent substances - thought and extension - was to produce the impossible dilemma of trying to explain how those two substances interact as body and mind either in human beings or in God. Spinoza had tried to solve the dilemma by saying that there is only one substance with two knowable attributes, though and extension.
But to reduce all reality to a single substance was to lose the distinction between the various elements in nature. To be sure, Spinoza spoke of the world as consisting of many modes in which the attributes of thought and expression appear. Still, Spinoza's monism was a pantheism in which God was everything and everything was [art of everything else.
To Leibniz, this conception of substance was inadequate because it blurred the distinctions among God, humans, and nature each of which Leibniz wanted to keep separate. Paradoxically, Leibniz accepted Spinoza's single-substance theory and his mechanical model of the universe. However, he presented such a unique theory of this one substance that he was able to speak of the individuality of persons, the transcendence of God, and the reality of purpose and freedom in the universe.
Extension versus Force. Leibniz challenged the fundamental assumption upon which both Descartes and Spinoza had built their theory of substance, namely, extension implies three-dimensional size and shape. Descartes assumed that extension refers to material substance that is extended in space and is not divisible into something more primary. Spinoza, too, considered extension as an irreducible material attribute of God and Nature.
Leibniz disagreed. Observing that the bodies or things we see with our senses are divisible into