In the state of nature, says Rousseau, man's life was essentially animal. The harsh existence of the forests made him robust, agile, with keen senses and little susceptibility to diseases, most of which are born of civilised life. His intellectual activity in these times was nil: "the man who meditates is a depraved animal". Living like this, man was happy and his only passions were natural instincts, easily satisfied (thirst, hunger, sexual reproduction, preservation). This is, in fact, the crux of Rousseau's argument: nature did not destine primitive man for life in society.