Time travel stories are lots of fun, but they are famously riven with paradoxes. And that can make it hard to enjoy them. If the future influences the past, is it not then past to that past, and so not future at all?
Such apparent paradoxes arise from a misconstruction of causation. They appear when we misconstrue causation by reducing it only to its efficient and material factors. This is the quintessentially Modern error; which is to say, the nominalist error. Efficient and material causation are essentially temporal, which is to say, strictly mundane (cave: so far, at least, as I have yet understood them). But causation is not limited to effect and matter. There are also, of all events, formal and final causes. And these are not temporally pegged; are not materially or efficiently pegged.
Whereas a concrete mundane thing has some spatiotemporal locus – whence arises its material and efficient causes – its formal and final causes do not. They are, rather, eternal and universal.
That’s why nominalism misses them. For, nominalism rules out real universals, real forms that have final properties. It cannot therefore adduce them as causal factors. It can, rather, recognize only material and efficient causal factors originating in mundane actuals. Nominalism then tends implicitly and directly to materialism, and scientism.
Nominalism tends to stupidity.
Forms and their final ends in other forms (every form is characterized in part by an urge toward the realization of some other forms) are eternal, and arrive for their material efficient mundane instantiations from a non-temporal source. They arrive at any given here and now, that is to say, from a source that is not only there and then – though it is that, to be sure – but is also always, and everywhere. They arrive from a temporal address that is eternal, and a spatial address that is universal. Thus their primordial temporal address is the future, and likewise also the past; for it is eternity. Likewise is their primordial spatial address everywhere; for it is ubiquity.
Formal causes, then, and their final urges, appear within causal systems – within, i.e., extensive continua such as characterize our own world – from without those systems. Formal causes, and their final urges, appear to us then at first devoid of spatiotemporal vector. They appear, that is to say, not only from within the corporeal world – from within its space, and from within its time. They appear rather from the environing context of this world’s spatiotemporal extent.
Mundane events then arise in the first instance from a transmundane basis.
What this means in practical terms is that their causal inputs are not limited to those of their actual mundane past. To the extent that a mundane event is informed by factors never yet manifest in its mundane past – i.e., to the extent that it is a truly *novel* event (which is only to say, to the extent that it is in fact an event in its own right, and not a mere aspect of some other apparently prior apparently different event) – it is caused by factors that have no temporal address.
Notice now that – provided it is real – a causal factor that has no temporal address can be found at all temporal addresses.
Consider then that, as having all arisen originally from a matrix of timelessness, all events whatever have “everywhere and everywhen” as the first and implicit argument of their loci; as, so to speak, the matrix within which, and by which, the vectors of the other arguments of their loci are specified in the first place.
To make that a bit more clear, consider a two dimensional Cartesian coordinate system. The locus of a point P in that system is specified by two arguments: its projection on the x axis, and its projection on the y axis (for, P is the projection of certain conjoint values implicit in the x and y axes of the system space; is a projection of certain formal properties of the system space). The address of the locus of P in the coordinate system – which is to say, in a prior extent or volume (spatial or temporal or both) – is specified by some values of x and y. When we then say that the first and implicit argument of P is “everywhere and everywhen,” what we mean is simply that P is located *in that coordinate system.* The first argument of the specification of P is the specification of the x and y axes. And these are prior to any P.
P(x, y) is located at the intersection of projections of x and y for some values of x and y. The first argument of the locus of P, then, is “(x, y),” for *any* values of x and y. Until the x and y axes are specified, there can be no values of x or y in P(x, y).
What this means – one of the things this means, among many others – is that, as having originated primordially from a locus of ubiquity along all extensive dimensions, each new event has arisen – at least in part – from factors that shall “cook out” of the process of becoming – which is itself prior to time, and thus atemporal – with spatiotemporal addresses located in its future.
Some of the factors of E are spatiotemporally located in what shall, mutatis mutandis, be its future.
Thus there is no paradox involved in so called “backward causation.” Causation can be known and understood as backward (or, for that matter, forward) only ex post facto. Is there something of event E that has never yet been seen anywhere in its world? It is insofarforth caused by factors prior to its time, transcendent thereof, and therefore located both in its past and in its future.
Notice then that every distinct event E is to some extent novel – or else, it could not be picked out as an event, at all. To that extent, its causal factors may as accurately be said to arise from its mundane future as from its mundane past.
All temporal events cook out of a matrix that is prior to time, and transcends it. Their temporal addresses are late aspects of their development, specified only in their final completion, when they have attained full definiteness. Only then can they be truly said to be, and so to have properties such as causal relations that are spatial or temporal (or anything else).
This is no controversial statement. Indeed, it is virtually tautologous. It is to say no more than that an event E(t, p) cannot have happened at time t and place p until it has there happened.
At every moment of their adventures, Doc and Marty are cooking out of a transtemporal matrix, and from the transtemporal perspective of their origination, all those moments cook out all at once, and together. There is no paradox.
Things must arrive as a coherent whole, not just across all space, but across all time. Otherwise, they could not arrive at all.
PS: All that said, and granting that some irreducible budget of the causal factors of any mundane event must arrive to it from temporal loci addressable in its future, travel backward in time may nevertheless not be practically possible. To the extent that you find yourself already located at some time t, it is probably not possible for a moment of your personal future to be located in your personal past.