Palgrave foundations series

by Bryan Greetham

Philosophical issues

Philosophical issues can be found in any number of concepts, and can be explored in seminars, lectures and your coursework. Use the following material to consider the questions that can be raised by differing concepts.

Space and Time

The philosophy of space and time is more closely related to the natural sciences than perhaps any other branch of philosophy. For those interested it offers a range of philosophical issues that are fascinating topics for papers and essays. To make it easier for you to select the kind of philosophical issue you might consider to research and write about I have listed below some of the most interesting philosophical questions that have troubled philosophers in the past and continue to do so:
  • whether it is proper to treat space and time as real things (Newton);
  • whether it is possible that there could exist empty space and eventless time;
  • whether our conception of our world as spatially and temporally extended beyond us is a function of an a priori scheme we impose on reality rather than of reality itself (Kant);
  • whether it is proper to think in terms of time flowing, or of the present existence of past events;
  • whether the asymmetry between the past and future is logically inviolate (necessarily true), thereby making time travel logically impossible, or only contingently so.
Among the more interesting problems that arise from the physical theory are:
  • what are involved as a result of observation and what as a result of convention when we measure spatial extension and temporal duration;
  • what sense does it makes to talk of space as having a given topology (shape) or even a finite size;
  • what are the implications of the two theories of relativity for the relationship between space and time.
Absolute vs. Relational theories

Perhaps the most interesting problem that presents some intriguing philosophical ideas is the opposition between those who advocate absolute and relational theories. An absolutist takes Newton’s metaphor of the container seriously. In other words he regards space or time as real things, containers of infinite extension or duration within which the whole succession of natural events in the world has a definite position - but in which they could have had another, had the whole process started earlier or in a different place. Similarly things may really be at rest or really moving, and this will not simply be a matter of their relations to other objects changing.

Central to this issue is whether space and time are independent of the objects in them, as the absolutists claim, or are they merely sets of relations between objects, so that it doesn’t make sense to talk of absolute directions or absolute motion? The notion of empty space suggests the corresponding notion of time without change.

The first serious opposition to Newton’s container theory came from Leibniz. In his metaphysical theory absolute space vanishes partly because reality, being composed of non-extended mental things, is not spatial at all. Similarly, Kant argues that our interpretation of our experience, as that of a spatially extended world, is an act of the mind - things in themselves (the noumenal world) have no spatial properties.

There are, however, more moderate relationists who try to preserve the reality of space or time by interpreting propositions about them as asserting nothing but relations among ordinary material things - in other words the container is not logically distinct from the things it is said to contain. The obvious obstacle here is that the relations involved are sui generis (i.e. of its own special kind, the only one of its type that cannot be explained in terms of anything else). So in this case you are forced to assume that spatial and temporal relations are special forms of relations, which cannot be described relatively in terms of something else, so it doesn’t appear that we have gained anything.

The Passage of time

Another puzzling philosophical problem is that of the ‘passage’ of time. It is almost irresistible to think either in terms of its flowing or of our moving through it. But, if so, we seem to imply that it could flow faster or slower - but then with respect to what? It’s hard to describe the ‘passing of time’, for whether time itself flows or we move in time, how fast do these things happen? They seem to need a second-order time to occur, but this makes doubtful sense, and anyway leads to a regress. If you have a second-order time, does this not equally require another second-order time to measure the flow of that time, and so on?

The measurement of time

Time, more than space, has seemed not to be real or measurable because most, if not all of it, so far as it consists of periods rather than moments, seems not to exist at any given moment, and what fails to exist nowhas seemed less real than what merely fails to exist here.

In recent times Einstein’s work has made the task of measuring time even more difficult. Einstein’s special theory of relativity treats space and time together as space-time. The main point of this is that in certain cases one event’s preceding another depends on the observer’s motion relative to the two events, and motion involves both space and time.

Philosophically the fundamental shift in Einstein’s special theory of relativity is the view that a judgement of the simultaneity of two events corresponds to no unique physical reality. It would do if it were possible to synchronize clocks that are spatially apart. But it is not possible to do this without making assumptions about the speed of light. When these assumptions are made, events simultaneous relative to one observer are not so relative to one in motion with respect to him. This seems to support the tradition in philosophy that sees time as a subjectively imposed ordering. But the precise implications of Einstein’s work are still controversial.

Time travel

Another question concerning space and time is whether they are parallel, in the sense that all, or nearly all, that can be said of one can be said of the other.

If a thing can move around in space, is it not possible for a thing to move around in time also?


  1. Could something exist which is not in space and time?
  2. Does time really pass, or are we aware of its passage only as a result of our experiences?
  3. Is the notion of time-travel self-contradictory?
  4. If all motion and change ceased would time continue to pass?
  5. Is it possible for time to be cyclic?
  6. Are time and space just constructs of our own minds?
Recommended reading:

Smart, J.J.C. (ed.) Problems of Space and Time (New York: Macmillan, 1968) (London: Collier-Macmillan, 1968)

Hoffmann, Banesh. Albert Einstein: Creator and Rebel (New York: Plume, 1972)