backward causation in defence of free will

Mind Association

Backward Causation in Defence of Free WillAuthor(s): Peter ForrestSource: Mind, New Series, Vol. 94, No. 374 (Apr., 1985), pp. 210-217Published by: Oxford University Press on behalf of the Mind AssociationStable URL: http://www.jstor.org/stable/2254746 .

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Backward Causation in Defence of Free Will1

PETER FORREST

In 'The Incompatibility of Free Will and Determinism' Van Inwagen2 relies on the impossibility of someone's rendering false a proposition concerning a state of affairs that obtained before that person's birth. This suggests that those who wish to defend Compatibilism should seriously consider the possibility of affecting the past. Now I do not want to defend the familiar compatibilist thesis that an act's being free is compatible with its being causally determined by earlier events. However, I do want to defend a less familiar version of Compatibilism, and I shall do so by relying on backward agency causation. I claim the following two theses are co-tenable:

The Free Acts Thesis: There are acts which are not causally determined by earlier events (and which are not random either), and which have physical consequences for which they are both necessary and sufficient in the circumstances.

The Iron Laws Thesis:3 Every physical event is causally determined by earlier physical events, in accordance with laws which, of physical necessity, admit of no exceptions.

When I say that the two theses are co-tenable, I mean that reasons for accepting one of them are not, thereby, reasons for rejecting the other.

I argue for this version of compatibilism not because I believe both the Free Acts and the Iron Laws Theses. I have considerable doubts about the latter.4Rather, it is that by establishing their co-tenability, I defend the Free Acts Thesis against one potential objection to it. For the Iron Laws Thesis is, I suggest, one of the strongest threats to the Free Acts Thesis which could arise from Scientific Realism. 5 But if the two theses are co-tenable, then this threat is averted.

1 I would like to thank Professor J. J. C. Smart for his helpful comments on an earlier draft of this paper.

2 Peter van Inwagen, 'Incompatibility of Free Will and Determinism', Phil. Studies, 27 (i975), pp. I85-209.

3 I follow D. M. Armstrong in calling laws which admit of no exceptions in any circumstances, 'iron laws'.

4 I am somewhat sceptical about the existence of laws of nature. And even if they do exist, they might have exceptions.

5 Here I ignore the apparently probabilistic character of quantum mechanics. I do so for the sake of simplicity. I leave it to the reader to decide what difference it makes if the laws are probabilistic.



Backward Causation in Defence of Free Will 2I I

Both the Free Acts and the Iron Laws Theses need clarification. I shall say that X is causally determined by events Y, Z, etc. just in case:

(i) Y, Z, etc. cause X. (ii) The occurrences of Y, Z, etc. are jointly sufficient for the occurrence

of X.

Clause (ii) will be ensured if some laws of nature entail that if Y, Z, etc. occur then so does X. I require clause (ii) because a cause might otherwise be probabilistic and so not sufficient for its effect. I require clause (i) because an effect may well be sufficient for its cause; this will happen if the cause is necessary for its effect.

When I say that an act A has a physical consequence C for which it is sufficient in the circumstances, I mean that the act A is a non-redundant part of a cause of C. When I go on to say that A is necessary in the circumstances for C, I mean that if A had not occurred then C would not have occurred.

Nothing in this paper depends on a specific account of acts. But in case the reader thinks that an undetermined act would have to be random, I shall briefly explain why that is not so. If P acts, then, I claim, P himself or herself is the cause6 of various physical and mental events. So the various physical and mental events are not random, they have a cause, namely P. What, then, is suspected of being random? The only candidate is the occurrence of the causal relation between P and the events. The existence of this causal relation is uncaused, otherwise the act would not be free. But it is not thereby random. For the occurrence of a causal relation between agent and event is not the sort of item to which the predicate 'random' properly applies. Indeed, I take it that most atheists believe the laws of nature which govern causal relations between events do not themselves have causes. Are they to say the laws are random? Surely not. Likewise a free act is not thereby random because it involves an uncaused causal relation.

One final point of clarification: I have stated the Free Acts Thesis in a strong form, demanding that there exist free acts with physical consequences for which they are both necessary and sufficient in the circumstances. My reason for this is to exclude two parodies of freedom. The first, which I call the epiphenomenalist parody offreedom, would occur if there were free acts, but none with physical consequences. In that case, ignoring the possibility of telepathy, we would not be able freely to affect each other. Nor could we freely affect our environment. I exclude this parody of freedom by demanding that the free acts have physical consequences.

The second, which I call the pseudo-epiphenomenalist parody offreedom, and which is of doubtful coherence, would occur if our acts cause physical events, but they do so only in cases where the physical events would have

6 The causation here will be singular causation, as championed by Anscombe. See G. E. M. Anscombe 'Causality and Determination' in Metaphysics and the Philosophy of Mind: the Collected Philosophical Papers of G. E. M. Anscombe, volume Two, Blackwell, I98I, pp. 133-47.



2I2 Peter Forrest

occurred anyway. So our free acts will still make no difference to other people or to our environment. I exclude this parody of freedom by demanding that the free acts are necessary in the circumstances.

I

If human acts were nothing but physical processes, then, of course, by the Iron Laws Thesis, they would be causally determined and so, I assume, not free. Therefore the two theses are co-tenable only if materialism is rejected. However, in spite of the popularity of materialism I believe there are good reasons for rejecting it, although it is beyond the scope of this paper to list them. My version of compatibilism, then, is within the scope of the sup- position that human acts are not just physical processes.

I shall, for the sake of simplicity, adopt a rather strong form of Dualism, in which acts are thought of as non-physical processes in which someone causes a mental event. Acts are then thought of as having further physical consequences, namely the consequences of that mental event. The act also will have a physical correlate, namely the brain-events which are correlated with the mental event. Whether this physical correlate is thought of as a consequence of the act or not need not concern usyet. (It will turn out to be a consequence.)

Consider, then, an act A with physical consequence E, where A is not itself determined. The Free Acts Thesis asserts that such acts exist. By the Iron Laws Thesis, E has some physical cause C, which is earlier than A, and which is a sufficient cause for E. Now A and C are not merely different non- redundant parts of some sufficient cause of E. For C is a sufficient cause by itself: This raises the question: What is the relation between A and C, both of which are causes of E? It is not the case that A and C are both parts of a single cause. It is not the case that A and C overdetermine E, in the sense that each is sufficient without either being necessary in the circumstances. For A is necessary in the circumstances. Nor is it the case that C causes A which in turn causes E. For then A would not be undetermined. It is the difficulty of exhibiting a suitable relation between A and C which underlies, I suggest, the way the Free Acts Thesis and the Iron Laws Thesis appear not to be co- tenable. But the problem has only to be made explicit for the solution to become obvious: the chain of causes is not in the temporal order, namely, C, A, E. I admit that C causes the physical correlate of A (the appropriate events in the nervous system) which, in turn, causes E. But, I claim, when a person acts he or she affects the whole causal chain, stretching back into the past, as well as forwards into the future. The events C, the physical correlate of A, and E form a segment of that causal chain. And, to the extent that the person's reasons for acting explain the act, they explain why there is that causal chain including C and E, rather than some other causal chain-the one which would have occurred if the person had acted otherwise.



Backward Causation in Defence of Free Will 2I3

Notice that, instead of the Iron Laws Thesis, we might have supposed that there was a first physical event (a 'Big Bang') and that every other physical event is determined by it. Then, on a variant of my proposal, when a person acts, he or she affects the qualities of that initial event. And his or her reasons for acting go some way towards explaining those qualities.

My proposal, then, is that in acting in an undetermined fashion, I affect the past. That is how I reconcile iron laws with free acts.

II

I propose taking backward causation seriously. That is, I am not relying on the mere logical possibility of backward causation; I require it to be a tenable position. To show that it is, I have, at very least, to flesh out in a coherent fashion the position I have sketched, providing a conceptual framework for it. What I shall do is to begin with a way of looking at a more orthodox position, that in which the Free Acts Thesis is held, the Iron Laws Thesis is denied, and backward causation rejected. I then show how this more orthodox libertarianism can be modified to provide the appropriate framework for using backward causation in defence of free will.

Suppose, then, that the Free Acts Thesis holds but there is no backward causation. Then among the propositions which an agent has not the power to render true at a given time there will be many for which we think this is no mere lack of power, many which, we might say, not even God in that situa- tion, and at that time, could render true.7 If of necessity there were no backward causation, these would include all propositions about past events. Also I assume any propositions whose truth follows from those about past events and such laws of nature as there may be would also be of this kind. I say such propositions have their truth-values fixed8 before the time in question. If they are true they cannot be rendered false, and vice versa. By contrast there will, at least at some moments of time, be some propositions whose truth-value is not yet fixed. For if not, there could be no free acts.

Some truths are eternally fixed, that is, their truth or falsity is fixed at all times. Among these I include the truths of logic (and their negations), the proposition that God exists, some propositions about the structure of space- time,9 and laws of nature. Being eternally fixed is, I suggest, a species of non- contingency. The true eternally fixed propositions are necessary in a fairly weak sense.

The reader might like to interpret 'fixed-true at t' as 'true at t', or as 'necessary at t'. One of my reasons, however, for using the term 'fixed' is that

7 The mention of God here is only intended to help in introducing the concept of fixity. If God is eternal, He is not in situations at times.

8 I borrow the term from Mackie. See J. L. Mackie, The Cement of the Universe, Oxford, 1974, see pp. 178-85.

9 It is incoherent to say that nothing about the structure of time is fixed at some time. For if nothing were fixed, there would be no particular time at which it was not fixed.



2I4 Peter Forrest

I do not want to commit myself either way. It is a delicate matter whether what is necessarily beyond my power to affect is simply true now or is necessary now.

There is a straightforward possible-worlds model for fixity at time t. (But here, unlike Lewis,10 I shall assume the very same particular can belong to more than one possible world.) For each moment of time t, there is a set St of possible worlds. (Because they are all possible worlds, the laws of logic hold in all members of St.) Then a proposition is fixed-true at time t just in case it is true at all members of St. It is fixed-false at time t just in case it is false at all members of St. I take it that what has once been fixed is never unfixed thereafter. So we have the requirement on our model that if u < t (that is, u is earlier1" than t), then St C Su. A proposition is eternally fixed if it is true at all members of St. So if we require that for all t, all members of St have the same laws of nature, then the laws of nature will indeed turn out to be eternally fixed.

Suppose someone was free to act at time t. If u < t < v, then Sv ' Su that is, SU is a proper subset of Sv. For before the act there were events which were in the agent's power to bring about. If he or she did bring them about, then their occurrence became fixed. If he or she did not, then their non-occurrence became fixed. Free acts, then, result in a restriction of the range of candidates for actuality.

It is also part of the orthodox picture that no one can know the future except, perhaps, in so far as it is already determined. We can express this by saying that at time t, no one can know that p unless p is fixed-true at t. Knowledge entails truth-fixity. In terms of the possible-worlds model, all that X can know is that the actual world is one of St. X cannot know that the actual world belongs to some designated subset of St.

Using the concept, then, of fixity, we can summarize the more orthodox libertarian position by means of the following principles:

(I) What is once fixed is always fixed. That is, if u < t, then St C Su (II) Actions fix events. That is if X acts at time t and that action is

causally sufficient for the occurrence of event E, then the occurrence of E is fixed-true at all times after t. So the proposition that E occurs is true at all Su for all u > t.

(III) No one (not even God) has power over what is already fixed. That is if X acts at time t and X's act is necessary in the circumstances for the occurrence of E then the occurrence of E is not fixed prior to t. So if u < t the proposition that E occurs is not true at all members of Su.

(IV) No one (not even God) can know what is not fixed. 12 That is, if at t, 10 David K. Lewis, Counterfactuals, Blackwell, 1973, p. 39, p. 87. I' I allow here the possibility that we are considering u and t as points in space-time where u < t just

in case u and t are time-like separated and u is earlier than t. 12 I leave open the possibility that the truth is fixed because someone knows it.




X knows that p, then p is fixed-true at t. That is, knowledge at t cannot discriminate between members of St.

(V) All laws of nature,13 logical truth, and the basic structure of space-time are fixed at all moments of time. That is, they belong to all of St.

(VI) The past is fixed. That is, if event E occurs at time t, the proposition that E occurs is fixed at all times after t. Hence that proposition is true at all members of SU, if u > t.

To obtain the framework for using backward causation in defence of free will I simply jettison the principle that the past is fixed, retaining (I) to (V).

I have jettisoned (VI). In its place I propose the Iron Laws Thesis. Since all laws are eternally fixed, the Iron Laws Thesis tells us that if every physical event occurring before t is fixed at time u, then so is every physical event occurring at or after t. But I assume that, at least for some u, it is not the case that all physical events occurring before t are fixed at u. Hence I retain the Free Acts Thesis.

The possible-worlds model enables me to handle two prima-facie diffi- culties with backward agency causation. First14 there is the threat of accidental interference. Suppose I act freely and so affect what has already happened. And suppose you then act freely and affect what has already happened. Might not my free act bring about an event E and yours, by chance, prevent E occurring? What is to stop this absurdity arising in my account? The answer is that (I), namely the principle that what is once fixed is always fixed, prevents this absurdity. If my free act brings E about then, after I have acted, the occurrence of E is fixed, so yours cannot subsequently prevent E occurring.

It might be replied that interference could still arise if we act simultane- ously. My rejoinder is that two agents will not have the very same powers at a given time. (Intuitively I have power over my body, you over yours.) For each power to act which an agent has at t there will be a dichotomy between those members of St which would become the candidates for actuality if the power should be exercised and those members which would become the candidates for actuality if the power should not be so exercised. Thus we have a dichotomy between At and St\At representing a power of Y to act at t. Likewise we have a dichotomy between Bt and St\Bt representing a power of X to act at t. Since X and Y have different powers At =# Bt. Nor is At = St\Bt. For in that case X and Y would virtually have the same power in that X could bring about the very same effect which Y could, although in this case Y would bring it about by refraining from acting, while X would bring it about by acting. Hence none of At n Bt, At n (St\Bt), (St\At) n Bt

13 If the laws of nature are themselves the result of God's act this needs qualification. But I am concerned here with human acts and so ignore this qualification.

14 Due to Professor J. J. C. Smart.



2I6 Peter Forrest

and (St\AJ) n (St\Bt) are empty. So whatever X and Y do there is a possible joint outcome of their acts. Interference never occurs.

The second difficulty is the basis of many arguments against backward causation. 15 It is this: What is to stop my observation of a past event E being part of my reason for acting, where E is the effect of that act? For example, suppose I observe my own brain-waves and they are ghastly. I infer I am sick and I need the services of an expert neurophysician. So I go to one. But it so happens that my having those ghastly brain-waves is an effect of my subsequent decision to see the neurophysician.

Causal or explanatory loops of this sort are intolerable; I grant that. But what is to stop them? On my account principles (III) and (IV) prevent such loops occurring. Either it is already fixed, when I decide to go to the doctor, that the brain-waves occur, or it is not. If it is, then their occurrence cannot be the effect of my decision. If not, then I cannot observe the brain-waves. So in neither case is there an explanatory loop.

I conclude that there is a coherent conceptual framework for backward agency causation, based on the concept of fixity.

III

Coherence is not, I think, enough for tenability. So I shall conclude my paper by examining two further lines of criticism of my proposal.

The first is an appeal to common sense. It is common sense that we cannot affect the past. But, I claim, I can explain away this common-sense opinion. Why then, is it common sense to reject backward causation? Part of the answer, no doubt, is a confusion between affecting and altering. We cannot alter the past. But then we cannot alter the future either, although we can affect it. However, I take the common-sense rejection of backward causation to be, for the most part, quasi-empirical. It is based on a thought- experiment. Think how you would set about affecting the past. By building a time-machine, perhaps? But how would you build one? We have no idea how to start. Yet, by contrast, we can work out how to affect the future in various ways-we just move our bodies.

This thought-experiment, however, at most shows that we have no way of manipulating the past in ways we could notice, that is, no way of deliberately bringing about some specified past event which we could observe.16 But I have not claimed that we can manipulate the past in this way. We have, at least in practice, no way of calculating the differences in earlier events required for the physical aspects of some action. So we have no way of bringing those events about by performing the requisite action. Moreover, I have assumed that we cannot affect the past in observable ways. (This follows from III and IV.)

" See, for example, Mellor's argument. (D. H. Mellor, Real Time, Cambridge, 1981, pp. 172-87.) 16 In 'Bringing About the Past' (reprinted in M. Dummett, Truth and Other Enigmas, Harvard, 1978,

pp. 333-50) Dummett reaches a similar conclusion. See especially p. 348.




Common sense, I suggest, is more concerned with manipulating our environment than with causation in general. And that explains why the strong thesis that there is no backward causation is part of common sense, when all that is warranted is the weak thesis that we cannot manipulate the past in observable ways.

Next, let us consider those philosophical arguments against backward causation which try to show that it could lead to causal or explanatory loops. I have already pointed out that the principles (III) and (IV) listed above exclude such loops. None the less, there might be some force in these arguments. For they show that I am committed to principles (III) and (IV), or some similar principles. I cannot jettison those. So if there were empirical evidence, or further philosophical argument, against one of these principles then I would be in trouble. Now principle (III), which restricts our powers to act, seems immune from such threats. But principle (IV), restricting what we can know, looks more vulnerable. Isn't it, in principle, empirically possible to observe the immediate past in whatever detail we like? And would not those observations, together with complete knowledge of laws of nature enable us to retrodict past events with complete confidence?17 If so, then either we can, in principle, know what is not yet fixed or the past is now fixed. But I have rejected the fixity of the past, so there seems to be an argument ad hominem against my principle that we cannot know what is not fixed.

My reply to this line of criticism is to deny the empirical possibility, even in principle, of observing the immediate past in sufficient detail. For even if quantum mechanics is replaced by some deeper deterministic theory, Heisenberg's Uncertainty Principle would still, I think, hold as a limit to what it is empirically possible to observe. For, considered as such a limit, it makes precise the vague empirical generalization that the greater the detail with which you want to observe position, the greater the energy you require, and hence the more you disturb the system being observed. Such dis- turbances prevent a second observation of position being accurate, and hence the observation of momentum. Therefore this limit to what it is empirically possible to observe would only be threatened by the discovery of a radically new way of constructing a microscope, one that used arbitrarily small amounts of energy to obtain arbitrarily great accuracies for the position of particles. But there is no evidence that there could be such microscopes. My proposal, then, is fairly secure against empirical evidence.

Department ofPhilosophy PETER FORREST

The Research School of Social Sciences The Australian National University GPO Box 4 Canberra, ACT 260I Australia

17 The Iron Laws Thesis ensures that we could predict with complete confidence. If we assume the laws are time-reversible, as they seem to be, we could retrodict with complete confidence too.



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