A quote from Robin George Collingwood, An Essay on Metaphysics (Revised Edition with an Introduction and additional material edited by Rex Martin).
p. 294-295 “A man is said to act ‘on his own responsibility’ or ‘on his sole responsibility’ when (1) his knowledge or belief about the situation in not dependent on information or persuasion from any one else, and (2) his intentions or purposes are similarly independent. In this case (the case in which a man is ordinarily said to exhibit ‘initiative’) his action is not uncaused. It still has both a causa guod and a causa ut. But because he has done it for himself, unaided, the double work of envisaging the situation and forming the intention, which in the alternative case another man (who is therefore said to cause his action) had done for him, he can now be said to cause his own action as well as to do it. If he invariably acted in that way the total complex of his activities could be called self-causing (causa sui); an expression which refers to absence of persuasion or inducement on the part of another, and is hence quite intelligible and significant, although it has been denounced as non-sensical by people who have not taken the trouble to consider what the word ’cause’ means.”