I have argued (e.g. here and here that the notion of a ‘truthmaker’ leads to an infinite regress. If there is such a truthmaker, an entity that makes a proposition like ‘Socrates sits’ true - let it be A - then it comes into existence when Socrates sits down, and ceases to exist when he stands up. But 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.
A similar problem attaches to the idea of representation (and at bottom, I believe, it is the same problem). Can the trueness or faithfulness of a representation – itself be represented? We say a picture is a true or faithful representation of what it represents. Aquinas says that truth is the adaequatio - literally the ‘equality’ or perhaps ‘adequacy’ – of thought to reality. This is like the modern concept of a ‘mapping’ or even ‘correspondence’ is similar – imagine the thought being like a picture or map that we could lay against the reality and match each element of the map against an equal and corresponding element of the reality that is mapped. But how do we represent the accuracy or ‘equality’ of the representation itself? The accuracy or trueness of the representation is itself an aspect of reality, and must be captured, but is not itself a feature of the representation. For accuracy is a relation, and the representation is only one term of the relation.
To represent the accuracy, we need a further representation – imagine a picture of both the represented object and the representation, with mapping lines drawn between the corresponding elements. But then this is also a representation. To represent its accuracy, we would have to represent it together with the two objects it represents, together with further lines joining both the mapped elements and the mapping lines. This is something too complicated to draw or even to imagine, but even that would not be enough, for we still have a representation. The accuracy of this must also be represented, and so on ad infinitum.
The problem is inescapable. If we buy the idea of a ‘truthbearer’ (a proposition, a thought, whatever), the idea of a ‘truthmaker’ comes with it. The truthbearer is one term of the relation, the truthmaker is the other. But the truthmaker can’t be the other term, because truth is a relation, and the truth includes the existence of the relation, as well as the existence of its two terms. Just as the accuracy of a representation cannot itself be represented, so the truth of a truthbearer cannot itself be expressed.