in his Existentialism is a Humanism: "man first of all exists, encounters himself, surges up in the world – and defines himself afterwards". Choice and sedimentation Jonathan Webber interprets Sartre's usage of the term essence not in a modal fashion, i.e. as necessary features, but in a teleological fashion: "An essence is the relational property of having a set of parts ordered in such a way as to collectively perform some activity". For example, it belongs to the essence of a house to keep the bad weather out, which is why it has walls and a roof. Humans are different from houses because unlike houses they don't have an inbuilt purpose: they are free to choose their own purpose and thereby shape their essence, therefore their existence precedes their essence. Sartre is committed to a radical conception of freedom: nothing fixes our purpose but we ourselves, our projects have no weight or inertia except for our endorsement of them. Simone de Beauvoir, on the other hand, holds that there are various factors, grouped together under the term sedimentation, that offer resistance to attempts to change our direction in life. Sedimentations are themselves products of past choices and can be changed by choosing differently in the present, but such changes happen slowly. They are a force of inertia that shapes the agent's evaluative outlook on the world until the transition is complete. Responsibility When it is said that people define themselves, it is often perceived as stating that they can "wish" to be something – anything, a bird, for instance – and then be it. According to Sartre's account, however, this would be a kind of bad faith. What is meant by the statement is that people are (1) defined only insofar as they act and (2) that they are responsible for their actions. To clarify, it can be said that a person who acts cruelly towards other people is, by that act, defined as a cruel person and in that same instance, they (as opposed to their genes, for instance) are defined as being responsible for being this cruel person. Of course, the more positive therapeutic aspect of this is also implied: You can choose to act in a different way, and to be a good person instead of a cruel person. Here it is also clear that since people can choose to be either cruel or good, they are,