In philosophy we have the seemingly innocent concept of reference. To what do you allude to (the word 'allude', itself being a concept). But when we talk about a reference we must first consider what a definition is because we tend to refer to things as being defined when in reality they are anything but.
For example, I see an ant. I refer to that object as an ant. I step on that object and obliterate it to the point where its constituent components no longer exist yet what can be said about my reference to that ant. What about any modifications to its environment that ant may have made. It did exist at some point in time, even if that point in time does nothing more than define my relationship to that ant (IE the ant no longer existed in its ant type form AFTER it interfaced with me).
Consider Abraham Lincoln. Is this a hard reference to a well defined object or a loose reference to something that no longer exists? So the concept of tense is central to the concept of a reference and the concept of a reference is strongly tied to the definition of an object.
Consider a hard reference something to the effect "I saw Abraham Lincoln remove his hat' versus a soft reference like "Abraham Lincoln's mother passed away today".
Since Abraham Lincoln no longer exists we must rely on the definition of what an Abraham Lincoln was in order to understand what we actually have a reference to. In other words the reference may refer to something which exists in one of two tenses; exists, or does not currently exist. There are many other dimensions we must consider like 'is in my present space', which we can examine later but for now let's limit ourselves to separating references into one of two groups; currently exists and currently does not exist. We can group a bunch of these attribute like things together later and refer to these things in a context but for now let's keep things simple.
So in the simple case where we have a hard reference to a well defined object (I saw Abraham Lincoln remove his hat today) we can now think about the difficulty in actually defining an object and face head-on the fact that in all such cases we must ultimately limit our concept of a definition in some significant ways.
The statement 'Abraham Lincoln was a human' is pretty much accepted fact. The exact definition of a human MUST be abstract. Not all humans are identical therefore our definition of a human must be based on physical attributes (like organs, etc) clipped at some level, which themselves are abstract concepts predicated on other abstract concepts like atoms. Think of the concept of a hand. Is there an absolute limit on the size (small or large) of a hand? Must it be operational? Must it be attached to a human? Must it be part of a biological organism? Do monkeys have hands? If all things must ultimately be composed of some atomic entity can we measure all things using this unit of measure? Can we say this love is stronger than that love because it contains more atoms? How many atoms does it take to make a love and in what configuration?
Regardless of how we go about this defining business (since absolutely defining something is technically impossible) what this definition must ultimately reconcile is what we accept as historical facts (effects) about this entity, regardless of entity tense. One might argue that once a reference no longer refers to a physical object it MUST reference the set of effects (we will call these 'accepted facts') this entity caused, however, one could also argue the set of effects this entity has accumulated over time must also be considered even when evaluating existing entities. Put another way you (and every other entity in the universe) are simply defined as the set of things you have affected even if the only thing you effected was yourself. References to you are either direct or indirect and refer to this set of facts.
So basically all references are weak and all objects are loosely defined. Such are the concerns of true AI.
