All these words refer to an essentially temporal reality. They speak to us of time and it is in time that they relate to the reality they refer to.
The past is the dimension of time that is more common to them. In the existence of a monument, document or a headstone it is the past that perpetuates itself. This does not stop someone from erecting a monument to the future. These monuments may exist but they are not the ones we find more frequently.
What we best know is the commemorative monument, of an event, of a person, both already passed away. Cities are filled with these kind of monuments. But even when a monument is erected to commemorate an event, it is dedicated to its protagonists: to the heroes of the Peninsular War, for instance, and so on.
The most obviously personalized monuments are those dedicated to the memory of an historical figure, like the Marquis of Pombal, for example.
A monument does not always commemorate a positive heroic historical event. Many times it is of the saddest events the monument perpetuates the memory. An example of this is the monument in the São Domingos Square in Lisbon that remembers the massacre that took place there in 1506. There an homage is paid to the victims avoiding forgetting them.
Moreover, a monument is almost always part of a fight for memory and against forgetfulness. That is probably why monuments today are hardly built. Electronic mediation devices, omnipresent in all our contemporary places, substitute the monument and make it dispensable.
The old habit, that was still common at the end of the 19th century, of resorting to a public subscription in order to erect a monument, would today be almost unthinkable. Unless it is for a football player like those statues that shine in the surrounding areas of some stadiums.
The religious monument will also still have some preference, like always. It is here that the monument suffers a certain fundamental ambiguity that religions have always taken into account.
The monument as an object of religious worship, while it is thought to be a representation of a divine figure, has its own negative prototype in the gold calf that the Hebrews worshiped in the desert while Moses received the slates of the Law on Mount Sinai. Hence the prohibition of building such monumental representations in some monotheistic religions such as Islam or Judaism. The same does not happen with Christianity, at least not in its Catholic version. Here the monuments, while representations of holly people, are themselves object of the same worship that is directed to the divinity they represent.
What could have happened to the monumental representations of Foz Côa? Were they the object of a religious cult; did they represent some sacredness; did they perpetuate in stone the memory of something worth it? We will probably never find out.
Given that the engravings of Foz Côa are monuments, these may diverge in a point from the ones we referred to. In Foz Côa the person who carved the representations may not have had the intention of them being monuments.
That is, not all monuments result from a monumental intention. There probably are monuments that are recognised as such by us today, but that originally did not result from intention like when someone orders a commemorative statue to be built.
Monument Valley, celebrated by John Ford Westerns, is a good example of this. Although we can also ask ourselves if there are monuments in nature or only possibilities that by analogy we try to anthropomorphise.
In a document this intentionality can also be detected although not always the one its author intended. That is, a contract that documents to the historian the first occurrence of the written Portuguese language, was probably not written with that intention. Although we probably are sure that the author wrote it intentionally to solve any everyday problem.
The document attests, directly or indirectly something that is not it. A wish, for example in a will.
The document also witnesses any event like when someone confesses a crime and this confession is written for proof.
A document almost always poses a problem which is that of authenticity. False or authentic, this is true, that is the question.
A document has the tendency and the intention to be true, that is, authentic and therefore valid when it expresses desires freely expressed in a contract, for example. The signatures that finalize it serve that purpose, to authenticate its truthfulness and authenticity.
However, it was not always like this, that is, a document did not always authenticate an expressed will. There were circumstances in which this authentication was done by word, a word “of honor”, in contracts. Was that word a document? Perhaps not, because of its evanescence. A document is something that is saved, preserved and filed by the testimony it gives to perpetuate memory.
Of a perpetuating memory is what the headstone usually ensures the remains of which it has the function to cover. A headstone is a stone that we frequently find in cemeteries. Its function is like that of a monument and of a document. On the one hand, it attests the identity of the person it refers to, it is a document, on the other hand, it commemorates the qualities of the person and perpetuates his/her memory just like a monument does.
A headstone is never a blank slate. The monument may not have any writing on it. It may even be prior to writing, as is the case of some prehistoric monuments, that is objects that we can now attribute or imagine the function of witnessing. Others are already contemporary to writing but do not use it, like the statue for example. Now a headstone is essentially made of writing. Its headstone nature is found more in writing that is engraved on it rather than on the stone that it is made of. Without writing there is no headstone. It becomes a simple stone. The stone is only relevant by the intention it demonstrates of eternity. Not all messages are headstone worthy, that is not all messages want to live forever in time. The qualification of “headstone” always applies to the language that is inscribed on it more so than to its support. By extension one could even say that any headstone sentence means exemplariness and fairness, making it worth perpetuation in memory that only the persistence of the stone could have given it before.
What is written on the headstone is directed towards the future and for it to be read. It may point out an event or a personality in its qualifications. Just like a monument does.
When a headstone and a monument point out an event, they do it for the future, it is true, but what they commemorate is the past, immobilised in an instant that it stays there in the chain of time marking what happened for future memory.
One can not say that the Foz Côa drawings are headstones, in the sense we have come to give the term. Or maybe they were. We do not know. The intention that was in their origin was probably not commemorative but rather celebratory or invoking like every religious image is still today.
As monumental representations, the Foz Côa engravings, supposing they had a religious nature, referred to the beings of the world just like they were then understood and desired.