It is important to consider man at the beginning, but it is not yet possible to follow him through all the stages of development. If you strip man of artificial faculties, you see an animal that is less strong and agile than other wild animals, but the most advantageously organized of all. Savage men live among beasts and raise themselves to the level of animal instinct. They are toughened by exposure to the elements. Natural man's only tool is his body, which is stronger than ours. In a one-on-one contest, savage man would easily beat civil man.
Hobbes argues that savage man is naturally intrepid: Pufendorf, Cumberland and others believe him to be naturally timid. Savage man is probably not afraid of anything, as he learns to recognize which beasts he can defeat. For example, the Caribs of Venezuela can defeat almost any animal. Other, more serious enemies are natural infirmities: childhood, illness and old age.
What is the role of medicine? Many of our ills are due to the excesses and passions of modern society. With few sources of illness in the state of nature, there is less need for doctors. We must beware of confusing savage man with civil man, as in mistaking domestic animals for wild ones. Being naked and without shelter is not a disadvantage to savage man, although it would be to us. Savage man sleeps much and thinks little. Self-preservation, whether through attack or defense, is his major care. To succeed in this, he needs robust senses.
We must also consider the metaphysical and moral side of man. Any animal is but an ingenious machine, to which Nature gives senses to operate and to protect itself. Man contributes to his own operation because he is a free agent, but is otherwise similar to the animals. Animals choose by instinct: man chooses by freedom. Man is therefore more adaptable than an animal. The key distinction between man and beast is the faculty of perfectibility. This distinct and unlimited faculty is the source of all of man's miseries. It draws him out of his original condition and causes his enlightenment, his vices and his virtues to develop.
Savage man begins with simple mental operations: he can will or not will to do something; he can desire or fear something. Reason develops and perfects itself through the passions. We seek to know only because we desire or fear something. These passions result from our needs. Savage man has no needs, and his only passions come from nature. Food, sex and rest are the only good things for him: the only evils are pain and hunger. There is no reason for savage man to cease being savage. His needs are close at hand, and he has no idea of the wonder of nature, or any conception of the future.
A great gulf exists between sensations and knowledge, a gulf so great that it must have taken a long time to cross. Agriculture and fire are good examples. How could agriculture develop without an idea of property or possessions? Even if savage man were highly intelligent, what use would this be if it could not be communicated? What could man achieve without speech or language? When one considers the importance of language, one realizes that it must have taken many thousands of years to develop. The first problem is why language became necessary. It could not have developed in families, which did not really exist in the state of nature. The actual formation of language is still unclear, but Rousseau ignores this and focuses on how language was established.