His main saying was "Existence precedes Essence". According to Sartre, humans do not have any predetermined nature or course that they should follow. They can decide to do anything that is valuable to them. They have free choice and independent action. The human nature is shaped through these free choices and values. According to the Existentialist view, we create our own nature through our actions, desires, decisions, plans and ambitions.
His above slogan negates the traditional view where essence comes before existence and this is the centre of the conventional argument that human beings are born pre-endowed with a nature of their own. According to the pre-determined nature, the individual's chances, opportunities, values, concept in life and achievements are all pre-determined and he will accept life according to the predetermined nature guided by his characters and nature. There is very little he can do about it and alter neither the own nature nor the course it is taking. But Sartre argues against all of it. So, according to his Existentialism it is all in the hands of Man and his likes and dislikes that makes life's rulings. His arguments on being-in-itself and being-for-itself are grounded on this basic assumption. "I suppose that it is accurate to say loosely that being in itself is nonconscious being and that being-for-itself is conscious being. And, at least pragmatically, we may as well restrict being-for-itself to human being," says Howells (1992, p.49).
He says that the external world is connected to the state of being-in-itself and it is a way of existence, an unconscious one, neither passive, nor active, and has no capacity of transcendence. According to Sartre humans like to play God and have a compulsive desire to reach the status of being-in-itself, which means, an ardent longing to be the master of one's own destiny, to be identified in a gratifying way, and attain complete control over his own and other's existence. The difference between the two states is shown in the most simplistic way possible by Sartre.
His famous example of a waiter is very interesting.
A waiter in the caf thinks that he is a born waiter and nothing else. He thinks that the caf cannot work without him and he is the epitome of perfection in his job. But Sartre says that this cannot be so. He says a man cannot be a complete waiter the way an inkwell is an inkwell. This means, inkwell cannot be anything else other than inkwell, while the man can be many more things other than being a waiter. If he loses the job, or if he gets some other opportunity, he will be come a policeman, or a shopkeeper or a lawyer, or anything else. He could get into any other identity, many of them, one of which is being a waiter because a human being is constantly creating and recreating himself and adapting himself to any role that becomes a necessity of the moment. As inkwell is inkwell, the man is a man. The difference is man can adapt himself to many more identities; but he still continues to be a man which is the state of being-for-itself. In the state of being for itself, he does not have any fixed nature or essence. Actually he should focus more on being for itself instead of being in itself, and he commits this error constantly. While doing so, he becomes a