Does presentism have a future?
Many hold that the past and the future are not real in any sense, and that the only reality is the present moment. This philosophical position is prosaically called presentism. Presentism holds that since the past does not exist, we cannot make true statements about it, since these cannot refer to anything real.
Patrick Dawson writes, "Presentists do not believe that the past or the future exist. Presentists generally do believe, however, that one can make true statements about the past, and perhaps about the future. A great many attempts have been made to establish some system of presentist truthmaking that allows for past truths, even though no past exists to ground them. These attempts have been criticised heavily, since they often commit presentists to all sorts of unhappy ontological commitments or unintuitive truthmaking principles. [I] ... investigate whether presentists might do better by just denying that there are any past truths at all."
When we talk about "the past", what are we referring to? The past is no more; it does not exist. The only meaning one can attach to the past is that it is an interpretation that we humans (or other animals) place on records and memories existing in the present. So the past exists only in our minds. It is a model of how we see the world extending back in time.
If we accept that "the past" is a model, then what is it a model of? To answer that question it is useful to look at the four-dimensional block view of the universe. In this view, taken from physics, the universe is seen as a stack of sheets, where each sheet is the universe as it is at one moment of time, with the next moment lying above it. This is a static view of the universe in which nothing happens, with time seen as the vertical axis. Of course, given that we live in three dimensions, the stack holding all states of the universe would have to be four-dimensional, but it is probably best to think of each two-dimensional sheet as an analogy for the state of our three-dimensional world. Using the block model, we can see "the past" as being all of the sheets below the one we are currently in. So our view of the past is a model of some tiny part of some of the sheets below the one we are currently in. Thus according to the block model, it makes sense for us to create our vision of states antecedent to our current moment. A "true" representation of the past would be one that tallies well with the layers below.
Interpreting the past and modelling the future are inescapable human activities. Even animals make mental models of the world based on their past experience. Although the past is nothing but a model of what has happened, and one that exists solely in our minds, having such a model is a categorical necessity. Despite this, according to the hard presentist view, such a model is meaningless. According to hard presentism, it does not make sense to believe we have paid the electricity bill yesterday, or even a minute ago, as this is an event in the past and hence unreal. In other words, philosophy collides head-on with common sense.
My rule of thumb is that if a line of abstract thought leads to a conclusion that is patently absurd according to common sense then it should be examined carefully. The problem with presentism is that the present is just as much an abstraction as are the past and the future. The present may be defined as the state of the universe at the current moment. This is an abstraction, as it is not something we can directly perceive. All we can directly experience is the data that our senses provide us at any given moment, which is an infinitesimal fragment of the totality of what we think of as being the present. So if the presentists wish to be consistent they should admit that all that is real is the momentary experience of our five senses. That would render almost everything and everyone "unreal", including all of science and philosophy, presentism included.
What is even worse news for the presentist position, is that we can never actually experience the current moment. This is because all our senses give us delayed information about the world. Whether this delay is 0.1 or 0.0001 seconds is beside the point. What matters is that the actual present moment is like the horizon - a point we can never reach. It is useful to remember that the stars we see at night do not appear as they are now but as they were thousands or millions of years ago. We can never see the stars or our own sun as they are now; we always see the past. The same holds for all our ordinary sense impressions, though on a different time scale. So we are never in the present moment but always lagging behind it. Since we never experience it, the present moment is an artefact created by our minds. In effect, it lies in our future.
In conclusion, what we call the present is just as much a creation of our minds as are the past and the future. The present is not a directly experienced reality but a mental construct. In fact, we are condemned to live in a world of mental constructs. We cannot know the world directly, as our direct perceptions give us only small fragments, ie sensations. As babies we even have to learn to recognise shapes, as initially all that our visual system gives us are movement and colours. All of our so-called knowledge is the elaboration of a multitude of models. Without our mental constructs or models we would be unable to function as human beings. We need to believe that we will be alive in an hour's time, that we can make plans for the future and that our daily actions serve a purpose. All our ideas are pictures of the three fictitious entities called the present, the past and the future. Since the past, present and future are nothing but models held in human minds, it follows that any statement that we make about anything at all (with the exception of identifying a present sensation) is a statement about a model. So how do we rescue the common sense idea that statements about the past are meaningful? Given the above, a statement about the past is just as much, or as little, meaningful as one made about the present, since both are really about models in our minds.
What about accurate vs inaccurate versions of past events? How do we rescue the idea of truthfulness? One criterion is if there is evidence in the present that points to one account being more accurate than another. But what about cases where there is insufficient evidence to decide the matter? Take a simple case where two people differ in their report of a conversation that they took part in, where there were no other witnesses. One person lies about the conversation, while the other gives an accurate account. Operationally, there may be no way to discern who is telling the truth. Yet it is hard to dispel the notion of historical truth. The liar knows that his report is fallacious and the truth-teller knows this too. So both persons have a private model that holds the truth of the matter. What about cases where there are no human witnesses, does it still make sense to assert that something happened? Perhaps the criterion here is that the event in question has consequences in the present, and these are the evidence that validate the event, even if we are unable to discover its traces. What about events that leave no trace in the present? I think such events probably do not exist, or if they do, are very rare.
Even this does not seem satisfactory. It is hard to let go of the notion that whatever happened did actually happen, regardless of any present evidence, such as memories. Perhaps the reason is that we human beings are irrevocably welded to the past. Without our memories we become blank slates - like new-borns, who have no language, no identity and no knowledge whatsoever. So the perceived truthfulness of our memories is crucially important to us. Without a substantially reliable memory faculty we are not able to function as normal human beings, cf people with dementia. Almost all of our knowledge of the world as it is now is contained in our memories, which makes the past a necessary working model for us. We also need our knowledge of the past in order to think about the future.
Of course, this does not mean that our memories can be said to be accurate or truthful in an objective sense, only that our mental and physical well-being depend on some sort of consistency. We also need an operational belief in the reality of the past, ie the past is nothing but a necessary working model of the world. This reinforces what reason tells us: that although our models are only shaky constructs, we are obliged to trust them. It calls to mind Howard Skipper's dictum: "A model is a lie that helps you see the truth."
Even if our models are all fictions, we must live as though we believed them to be real. There is no other option. The paradox is that reason tells us that our models are not to be trusted, and also that we must trust them.
Although philosophy is a fine diversion and useful for exercising our brains, when it collides with common sense, it is the latter that should be given primacy, until proven wrong.