Assume all my representations are tenseless representations and I need to use them to act. Are these enough, representation-wise? Since we are talking about creatures which act at a time, for action, we need to coordinate the proposed action with time or else any success we meet in our endeavors will be a wild accident at best. So given tenseless information about a time at which I am located and need to act at, I need to be able to act reliably at that very time. This requires keeping track of the time in some way. To be reliable in coordinating tenseless temporal information with action, then, we need to make certain temporal information relevant in the proper way or action - or intention-in-action-producing at the relevant times. So, in other words, we need at least one clock-like-functioning system which somewhat reliably coordinates action with which times are appropriate to act at and so which tenseless representations are appropriate to act on. This system could take on multiple forms and, indeed, we may need more than one of these. Clock-like systems could include systems that act as timers, oscillators, accumulators, digital clocks, etc.
Now consider a speedometer. A speedometer represents a lot of different speeds. But that by itself is not its function - its function is to indicate (via the pointer) what the speed of the vehicle currently is. So lots of speeds are represented but only one in particular is represented as the speed of the vehicle - and this is done without explicitly representing anything but the speed itself. Now consider a carbon monoxide detector where a light labeled "Carbon Monoxide" lights up whenever the compound is present. Clearly, this detector represents carbon monoxide but its function is to detect the presence of carbon monoxide. So when the light is lit up, it represents carbon monoxide as present - even though its presence is not itself explicitly represented. This works even if the detector tokens a full representation which doesn't mention the presence of carbon monoxide, so long as the function of the system is still the same. So if the light is labeled "Carbon Monoxide is Very, Very Bad", the lighting up of the light and thus the system's coordination of the presence of the compound with the representation is still representing carbon monoxide as present despite this fact being extrinsic to the representation itself.
What we can learn from looking at these few examples is that if it is the function of a system to detect, indicate, or otherwise track that some F is G, and it does this by tokening a representation of F, it thereby represents F as G. Now apply this to clock systems. Clock-like systems can represent a lot of different times or be involved in coordinating times with representations which explicitly refer to a lot of different times. It is the function of the clock-like system to track the current time. And by doing so, it represents that time as being present or being now. So a clock-like system is essentially a tensed system - simply put, just a system for keeping track of the time. That is, we really do need tense after all - not simply tenseless representations.
What a tensed system like a clock in effect does is to attach temporal representations to the appropriate time in such a way as to be in a certain way infallible. This is especially apparent in the case of representations where time is not explicitly represented at all and yet which are still only about temporal matters (and are hence in this sense tensed) - the time enters into the represent implicitly or is represented by itself. An explicit NOW concept is perhaps at least partly a placeholder making explicit the implicit presence of the current time. Tensed systems and representations, then, constitute a kind of direct access to time that we need as agents to act.
If we have a system for keeping track of the time without necessarily requiring an explicit representation of time, it may be more economical for us to token representations which leave reference to the present time implicit. In that sort of case, an ordinary thought about the present time and one simply about how things are simpliciter or tenselessly may very well take the same explicit surface representational form – that is, there may be no syntactically present-tensed verbs at least at the explicit surface level. So we get things like 'Fred is cold' and 'Fred is human' where the first is to be interpreted tensedly whereas the second (arguably) is not (a less contentious example might be one involving a mathematical sentence). Yet both have the same surface explicit surface syntax.
In the tensed representations of this sort that lack a NOW or similar concept or locution, no explicit piece of the representation represents the time (the time of the representation itself does this). The temporal 'at t' parameter which is in the truth conditions is hence not explicitly specified, which is why tenseless and tensed representations of these sorts will look the same. In these present-tensed representations, it is the time of the representation itself (roughly) that enters as the value of the implicit parameter. In other, perhaps less primitive ones, we may have a sentence with an implicit temporal parameter that is not pointed at the present but where the value of the parameter is some time which is particularly salient or otherwise demonstrated. So 'Go to my house' may have the current time as its value - I want you to go now - or it may have some other time contextually specified - such as some time soon, or after you've picked up my laundry, etc.
As mentioned earlier, NOW perhaps, then, acts as something which makes the parameter itself explicit, often indicating the time of the representation but without specifying explicitly which exact time that is - it is a stand-in for that time, whichever it may be. So NOW can be used to explicitly disambiguate representations that can take one or more tensed readings and/or a tenseless one. This might explain part of the reason why NOW always takes wide scope in sentences (particularly modal or temporal ones), since it's really the implicit current value of the temporal parameter that enters into the semantics – the NOW simply indicates its presence or place in those semantics.
All of this perhaps explains part of why tensed views of time are so attractive or natural to many people (put aside whether such views are true or not) - since there is no surface difference between present-tensed and tenseless representations, it is easy to confuse being F at t (where t is the current time) with being F simpliciter. If there is no explicit parameter – just NOW as a placeholder – then it will be easy to confuse ‘being F’ with ‘being F now’. And since NOW is a relatively simple concept, irreducible to tenseless ones, etc., then if one mistakes properties of representations for properties of what is represented (or for properties of what is expressed) one will take it that NOW expresses a relatively simple property which is not reducible to any tenseless ones – that is, there must be irreducibly tensed properties. And not only that, since the reference of NOW shifts over time, given this same confusion we will get confused notions of tensed “temporal passage”. A kind of primitive use/mention confusion.
Additional note: NOW is, perhaps, thus different from PRESENT. PRESENT seems to mean something akin to LOCATED AT or IN THE PRESENCE OF. So 'A is present' "means" 'A is located at' or 'A is in the presence of'. Unlike NOW, PRESENT does not take wide scope. Since this sort of representation is tensed, what is really going on is that the temporal parameter which would complete the representation and tell us at what time A is located is left implicit. So PRESENT takes a temporal parameter like many other predicates and doesn't specify a time at all on its own but will pick up that parameter, like any other similar predicate, from that governing whatever clause in which it happens to be embedded. (Compare the difference in parameter between 'A is present now', 'A is present at noon', etc.)
