It makes no difference whether the occurrence in question is that of a nail being driven into a board or of a man being influenced to make a choice. The existence of causality is not dependent upon one's awareness or acknowledgement of its presence. Influences are always fully causal in nature. An influence that does not influence is not an influence. A cause which effects nothing and affects no one, is not a cause.
All genuine influences produce their own effects.
They make certain things necessary, even if they do not make other things necessary. The other things have their own causes. It is evident that whatever occurs for a purpose takes place due to a cause, for it is absurd to conceive of a thing of chance having a purpose. It is foolish, however, to think of this accounting as an occasion for divine retribution upon free will sin. Indeed, it would be impossible to give any account whatever for a free will or uncaused event, in the sense of giving an explanation for its occurrence.