A stone is free to be itself as long as it is not interferred with through some force acting to change it.
But if we are only free to be ourselves and not free to be other than ourselves, then there is no freedom to be ourselves, rather, being ourselves is the only thing we can do.
Example of being other than ourselves: Hitler does not merely decide to become Florence Nightingale but actually manages it.
This question really only makes sense post-Existentialism when the idea that we can make ourselves began its rather demonic grip on Western consciousness. I say demonic, because I see very little evidence that most people want to do such a thing. But it has become a mantra for our secular society:
Be what you wish, be what you want when all the people want is, as the recent blossoming of mass strikes show in the UK, is to have bread.
I see this mantra as merely another level in which man lauds himself. He is free in a way that no material object, like a stone or a rock, can be; and nor like any other animal can be. In Islam, the mountains were offered freedom but they refused but man agreed and he has been suffering ever since as it is a mixed blessing. But in his blindness to his own condition, he has made this freedom his principle, his method, himself: freedom, free markets, free thought, free will and free remaking.
Metaphysically speaking, you can only be what you are as you can be nothing else. This includes complaining about wanting to be something else as that merely means being such a complainer is amongst your attributes. And you are always free to express who you are to the degree that you have the art of self-expression. Such a gift does not belong to everyone. You can try, though; you can try ...
You argue for an essentialist position.
According to Existentialism (eg Sartre): existence precedes essence
The Sartrean claim is best understood in contrast to the scholastic thesis that essence precedes existence, i.e. a typical claim for this traditional thesis would be a human is essentially selfish, or that they are a rational being.
To Sartre, "existence precedes essence" means that a personality is not built over a previously designed model or a precise purpose, because it is the human being who chooses to engage in such enterprise. While not denying the constraining conditions of human existence, he answers to Spinoza who affirmed that people are determined by what surrounds them. Therefore, to Sartre an oppressive situation is not intolerable in itself, but once regarded as such by those who feel oppressed the situation becomes intolerable. So by projecting my intentions onto my present condition, "It is I who freely transform it into action". When he said that "the world is a mirror of my freedom", he meant that the world obliged me to react, to overtake myself. It is this overtaking of a present constraining situation by a project to come that Sartre names transcendence. He added that "we are condemned to be free".
To claim that existence precedes essence is to assert that there is no such predetermined essence to be found in humans, and that an individual's essence is defined by the individual through how that individual creates and lives his or her life. As Sartre puts it in his Existentialism is a Humanism: "man first of all exists, encounters himself, surges up in the world – and defines himself afterwards".
So according to existence precedes essence point of view, we are free to create ourselves instead of being free to be ourselves.
He, not busy being born, is busy dying.
Bob Dylan
I believe you are misconstruing self-identity. As Heraclitus says, you can never step in the same river twice, though paradoxically, we can refer to "the river" and conceive of "twice."
Similarly, we can point to "that same stone." Yet the stone is never "the same" and never isolated from "non-stone" forces that ceaselessly change it over time and space. For the stone, there is no "being itself," nor what we would call "freedom" from external forces and mechanical causality.
The self-conscious being, on the other hand, by definition entertains a concept of "itself" and the contradictions that define it by what it is not. Without this irreducible contradiction, we would not have desires, uncertainties, or entertain possibilities apart from what merely is.
Like the stone, we will constantly change, becoming other than we are or were. Yet we have presumably a capacity for freedom, a kind of second-order causality that allows us to pry apart and suspend mechanical causality and actualize the possibilities therein.
Obviously, Hitler can never "really become" Florence Nightingale, since these are particular and mutually exclusive subjects. But Hitler can access his subjectivity to be other than he is. This, at any rate, is a basic interpretation of what we mean by "freedom," though of course there are various determinists who would argue that we are subject to fate, destiny, or a physical determinism little different from the stone's.
