Torus IV by Eric J. Heller. "The dynamics of a system of two degrees of freedom involves two positions and two velocities... Thus, a system of two degrees of freedom 'lives' in four mathematical dimensions. If the motion of the system is not chaotic, it actually lives only on the surface of two-dimensional torus, which has the same topology, or 'shape', as a donut. The torus is, however, embedded in all four dimensions (a real donut has its two dimensional surface embedded in three dimensions)."

Because there simply is no objective way to characterize the present, the experiential now has no counterpart in the physical world. And because past and future are defined relative to the present, they too cannot be defined in physical terms. The temporal modes past, present, and future can be characterized only by how they relate to us as conscious subjects: through memory, through the present-tense immediacy of qualia, or through anticipation. In the physical world we may qualify events or states of affairs as past, present, or future relative to other events or states of affairs, but we cannot speak of the past, the present, or the future. The proper view of physical reality is not only what Thomas Nagel has called "the view from nowhere" — the physical world lacks a preferred position corresponding to the location whence I survey it — but also what Huw Price has called "the view from nowhen'' — the physical world lacks a preferred time corresponding to the present in which I experience it. The idea that some things exist not yet and other things exist no longer is as true (psychologically speaking) and as false (physically speaking) as the idea that a ripe tomato is red.

If we conceive of temporal or spatiotemporal relations, we conceive of the corresponding relata simultaneously — they exist at the same time in our minds — even though they obviously happen or obtain at different times. Since we cannot help it, that has to be OK. But it is definitely not OK if we sneak into our simultaneous mental picture of a spatiotemporal whole anything that advances across this spatiotemporal whole. We cannot mentally represent a spatiotemporal whole as a simultaneous spatial whole and then imagine this simultaneous spatial whole as persisting in time and the present as advancing through it. There is only one time, the fourth dimension of spacetime. There is not another time in which this spatiotemporal whole persists as a spatial whole and in which the present advances. If the experiential now is anywhere in the spatiotemporal whole, it is trivially and vacuously everywhere — or, rather, everywhen.