Now that Fall semester grades have been turned in I have a little time to do some blogging before things get really busy with (1) Christmas (12/25), (2) my wife and I bringing home our newborn adopted baby girl (12/26), and (3) my trotting off to the Eastern APA for job interviews (12/27-30).
I’d like to talk about spatial tenses. That's right, spatial tenses. Because we normally associate the word "tense" with time, associating it with space may seem odd, but in fact there’s nothing incoherent about it.
Consider the following:
Past tense: Yesterday, I ate a burrito.
Present tense: Right now I am sitting at my laptop.
Future tense: There will be a sea battle tomorrow.
In each case, the tense of the claim functions like a compass needle. It gives us a conceptual orientation by telling us what direction to go from the present moment to arrive at a specified event. The past tense tells us to work backwards from the present, at what is 'earlier than'. The future tense tells us to project forward from the present, at what is 'later than'. And the present tense tells us to consider how things are now, at what is 'simultaneous with' the present.
The essence of a tense, then, is that it provides directional orientation from a privileged reference point. In the case of time, this reference point is the 'now' or the 'present'. So-called tenseless claims contain no such point. For example, to say "There is [tenseless] a sea battle on 12/20/2007" I have to forget where I am in relation to 12/20/2007. If I allow myself access to information about whether that date is earlier than, later than, or simultaneous with 'now', then I've illicitly smuggled tense in through the back door.
To recognize spatial tenses all we need is a privileged reference point and a way of orienting things in space in relation to that reference point. Aristotelian physics includes just that. According to him, there is a privileged spatial reference point - the center of the universe - and a way or orienting things in relation to that center. Things can move 'toward' the center, 'away from' the center, or 'go around' the center. This shows that the notion of spatial tenses is not incoherent. Still, many people would doubt whether it is a useful notion post-Copernicus.
After all, it doesn't seem that there is any objective spatial reference point that we can identify and refer to. Perhaps there is an objective 'center of the universe', but even if that's so, do we have any way of identifying where is it? In the case of time we can identify the present by self-reflective introspection. But even there a question arises whether the present so identified is the present or merely a present? On the one hand, A-theorists believe that tense (in the temporal sense) is an objective feature of reality. According to them, there is an objective 'now' that we directly apprehend in the self-reflective immediacy of our own consciousness. Hence, we are in touch with the present. On the other hand, B-theorists deny the objective reality of tense. According to them, our use of tensed language merely reflects our subjective or egocentric perspective. For them, we cannot refer to the present, but only to a present.
In support of their position, B-theorists like to press an analogy between temporal and spatial tenses. In the first place, it seems that spatial words like 'here' and 'there' are merely subjective or egocentric. I say "Here I am" and you respond "Oh, there you are!" it seems clear that 'here' and 'there' merely serve to locate things in relation to the speaker. In the second place, it seems that 'here' and 'there' function exactly like the temporal words 'now' and 'then'. Hence, asks the B-theorist, why think that 'now' picks out the objective present when 'here' only picks out the speaker's location? Why not construe both terms in a subjective or egocentric way, such that 'now' simply means 'simultaneous with [this speech act, the time of this utterance, etc.]'?
Those are fair questions. It seems that the A-theorist has to either (1) identify an objective spatial reference point (but what?) or (2) insist on a brute difference between spatial and temporal tenses, with the former being merely egocentric and the latter not. The plausibility of (2) may be argued by pointing to differences in how we can orient ourselves in space and time. Space has three dimensions, which allows me to change position in relation to other things, to go elsewhere. This means that where I am is to some extent up to me. In addition, I can interact with other beings at other places (“Hey you, over there”). All this confirms the egocentric nature of ‘here’ and ‘there’. But time is different. I can't move around in time and go elsewhen, at least not until someone invents a functional time machine. When I am is not at all up to me. Nor can I interact with other beings at other times. I can only do so now. Of course, if a time machine could be invented - and that's a very big if - these disanalogies between space and time would collapse. But until then, it seems that the now constrains us as it would if it were objective, whereas the here does not.