On reference & Custom

When someone is called "John" in human culture it means that the word "John" is taken by speakers to replace the actual person John (who may be short and dark haired with a light hearted attitude) in verbal structures. When John hears his name he knows that he is involved in the conversation.

But this is only convention. John could just as easily refer to the person who is also called Mike. Now we enter the problem of identity loved by Elizabethan playwrites. Quite when we use the name John and Mike can only be determined by custom, context and circumstance. In an alien culture there may be complex formal rules governing when to use particular names that will seem random and of no sense to a human guest. Imagine explaining the old use of you and thou to an alien who doesn't have a concept of intimacy or informality!

Now isn't the same true of sentence themselves. It is customary to interpret a sentence that described the previous sentence as having eight words as meaning the sentence before this one. Were the customs of English different it might mean this sentence itself. Likewise a sentence that says that it has nineteen words might be customarily interpreted to mean the previous sentence.

What is true however is that to create a current point of reference we need some level of identifying the here and now. A sentence which says "the first sentence of this blog entry" must still make reference to the here and now even while not envoking itself. This shows however that "this sentence" is actually referring to itself only by use of an external here and now reference which is customarily accepted for the English language. It is certainly external self reference and so of little interest.

I need also be careful here of use/mention. A sentence can't actually refer to itself so easily because "this sentence" is just a quote and marks on a page. While this sentence is an actual sentence. Or is it because it doesn't quote itself so it is actually non gramatical within the rules of English.