The nature of time has been one of the major problems since antiquity. Is time well thought of as a flowing? If not, how do we conceive of its passage? What distinguishes the present from the past and future, or is there no objective distinction? What accounts for the symmetry between past and future? Can we make sense of timeless existence?

Defining time requires defining the background definitions with which we define time, while avoiding circular definitions: for example, ‘time is change’, and ‘change is what happens over time’. What if time is not just something that we count in observing change, but the ‘something is change’ that allows us to count. This forms the basis of physical conceptions of time used in sciences. Or we claim that time is independent of change and indeed of the universe, whereas someone else may explain that time’s progress is relative to the observer, which implies that the ticking of a watch depends on the faster its wearer is travelling, the slower time proceeds relative to other observers.

If we still rely on the perception of change to understand time, does that mean that an absence of change implies as absence of time? If there is no perception of time, does time still exist? Maybe time is indefinable and unreal, or we conceives time as purely mental or psychological, or argue that time is a necessary experience of consciousness, a category that we place upon the world. What if it is explained that we are not passive objects to time’s passing, but that we live through time which gives rise to the phenomenological study of duration.

Certainly, our consciousness of change is linked to how we understand time; hence it appears that sometimes if flows quicker than at other times. But we are then aware of the passage of some things which brings us back to physical time of the scientists by which we can both gauge our procession and the change in other things through time.

Are the past and the future real? To some only the present can be real, since that is all that we experience. That either means that past and future do not exist in some meaningful way and hence we would not have much to talk about, or the past is a separate category ‘was once real’ and the future ‘yet to be real’ both implying that the past and future are not real.

For instance, the cup to tea you need to make to ponder time further, does it presently exist? We know that it will exist and therefore will have existed, but what kind of existence do things in the future have? Are they the same as present and past? And what of my choice to make the tea, when did that arise? Was it always there? Waiting, or deep in my past? Conceiving time is similar to visualizing a four dimensional object: a quintessentially slippery process.