A truthmaker is something that makes a proposition true at a given time. When Socrates is sitting, so there is a truthmaker that makes ‘Socrates is sitting’ true. When he stands up, there is no longer such a truthmaker: it ceases to exist.
I accept Maverick’s arguments, which I discussed briefly here, that Socrates himself cannot be the truthmaker for ‘Socrates is sitting’. For Socrates is sometimes not sitting (for example, when he stands up). Socrates remains identical with himself, but fails to be identical with any currently existing person.
But, pari ratione, by equal reasoning, I reject the idea of a truthmaker altogether. If there is such a truthmaker, let it be A, it comes into existence when Socrates sits down, and ceases to exist when he stands up. If it were something real – let’s say a candle flame, which comes into existence when we light the candle, and ceases to exist when we blow it out – then there would have to be a further truthmaker for A existing. I.e. the sentence “A exists” can be true or false, and so requires a further truthmaker B, that makes it true when B exists. But then “B exists” requires yet another truthmaker, and so on ad infinitum. That is absurd. Therefore, there are no truthmakers.