The structure Socrates has humanity is here considered to be a real relation. This is certainly true when we have in mind the actual states of affairs in extramental reality. There, Socrates, as a supposit, certainly is related to the objective formal content humanity in the way of possessing this content (necessarily).
Now it is the contention of Intentional Logic that this real relation, as it exists (or existed) in extramental reality, cannot be genuinely intended by the proposition ' Socrates has humanity ', but only by the proposition ' Socrates is human '. This, as it is argued, because ' Socrates has humanity ' when considered to be a sign, is a real relation, which has therefore first be known before it can serve as a sign, which means that it is not an intentional sign but an instrumental sign.
Although it is clear that as a really existing sequence of words ' Socrates has humanity ' is an instumental sign (the words must first be read or heard), it is not so clear how it is with the corresponding mental state that is implicitly evoked (while the corresponding extramental fact is explicitly realized [when the words are read or heard] ).
Intentional Logic maintains that this mental state, if indeed it appears in the form of ' Socrates has humanity ' (and not in the form of ' Socrates is human ' ) embodies a real relation that is somehow structurally similar to the corresponding real relation as it is in extramental reality.
How could this be? Of course we don't know. Maybe it has to do with conscious or unconscious imagination, which as such is a mental model or picture of the corresponding extramental relation. If this is correct, then we indeed have to do with the presence of a real relation in the mind. And this real relation (image) is then just an instrumental sign pointing to the extramental relation which is more or less similar. And, if this were the only way to point to that extramental relation we would never have a means of verifying whether this image actually resembles the extramental relation or whether it is similar to it at all.
Fortunately, however, we do have another means at our disposal, which, in contrast to the instrumental sign, really intends our extramental relation, namely the subject-predicate proposition ' Socrates is human '.
But the problem here is the status of the proposition ' Socrates has humanity ' (and all other propositions that assert real relations) when it is internalized in the mind. As a preliminary solution of this problem we have considered the result of this internalization to be an image or mental model, and as such to be an instrumental sign.
In mathematical Logic one adheres to the same solution. One even generalizes it to cover all propositions, including the truly intentional ones, the subject-predicate propositions. So mathematical Logic makes all signs to be instrumental signs.