D'Holbach believed that the misery he saw in mankind around him was caused by religion and its superstitious beliefs - that there was a God who controlled destiny and would reward and punish individuals. The System of Nature was written to replace these delusions with a schema of understanding based solely on the physical workings of nature. For d'Holbach, the soul is only the physical body, understood from a certain point of view, which dies when the body dies. All the events and the nature of the world can be understood in terms of the motion and properties of matter; even the tiniest causes contribute to huge events - a simple change in the diet of an Emperor (or some other such insignificant cause) might have been capable of saving kingdoms , he suggests. For him, nature's laws are fixed and necessary, and if Man wants to find happiness it is best to accept this - if governments want to rule wisely they should base themselves on this principle. Man's fear of death and desire for immortality should be resisted and those in power should not be allowed to play upon these passions.