Thus her actions violate her prescriptions. This constitutes a kind of proof of the view that some rules, rather than no rules, should be applied. This kind of proof is the only kind we can expect to have, when someone chooses to deny rules of logic. To form a logic that will allow sentences to refer to one another, we will add formulas to classical logic. Reference to sentences is not possible in classical logic, but is a feature of natural language.
Honey is sweet.
If sentence A is true then honey is sweet. A is true. We can call this pair of sentences an instance of the Tarskian schema. We first consider the case of reference to a sentence with known content. If we have the ability of formulas to refer to other formulas, we can use it to set up a loop of sentences, each referring to the next.