  If propositions are unstructured and distinct from sets, there are several possibilities for explaining their identity conditions. First, identity conditions might be specified in terms of possible attitudes. One possibility is this: P=Q if, necessarily whoever believes (asserts, denies, etc.) P believes (asserts, denies, etc.) Q, and vice versa.  Second, proposition identity might be reduced to property identity in the manner of Myhill (1963) and Zalta (1983).  Thus, Zalta (1983, 72) offers the following definition of proposition identity: &lt;p&gt;=&lt;q&gt; if and only if the property of being such that p is identical to the property of being such that q.  A third proposal, not incompatible with the second, is to explain proposition identity in terms of the “free generation” of propositions from a stock of certain non-propositional entities, e.g., individuals, properties and relations, by algebraic operations (Bealer 1982, Menzel 1986, Zalta 1983 and   1989).[10]  Although propositions on this approach are unstructured, each proposition may be represented by its “construction sequence.” To avoid identifying &lt;Hesperus is beautiful&gt; with &lt;Phosphorus is beautiful&gt;, the relevant inputs cannot simply be Hesperus (Phosphorus) and the property of being beautiful. A well-known strategy to cope with this problem, due to Frege, is to appeal to different modes of presentation associated with the different names, each contributing something different to the proposition expressed.  However, these modes need not be understood as complex properties uniquely exemplified by referent of the name. For instance, Bealer (1998) invokes what he calls “non-Platonic” modes of presentation.  Whether these non-Platonic modes of presentation are understood as words, as causal chains of word use, or in some other way, the important point is that the mode associated with ‘Hesperus’ will be different than that associated with ‘Phosphorus’. Zalta (1989) introduces propositions with abstract constituents to do the work of these modes. On Zalta’s view, such singular propositions are built out of abstract individuals that encode the cognitive content of names. Since these abstract individuals encode this cognitive content, there is no need for the referent of the name to instantiate it, and a fortiori no need for the content to be a property uniquely instantiated by this referent.  For more on encoding vs. instantiating, see section 6 of the entry on existence.  Thus, these theorists hope to use the metaphysical tools of these algebraic accounts to accommodate some of the key Fregean intuitions about differences in propositions expressed while avoiding difficulties with the Fregean doctrine of sense.