Lewis’ Counterfactuals
In the debate over causation, one of the notable names is David Lewis. It is his work on
counterfactuals, stemming from Hume, that is worthy of such attention. Two of Lewis’ works
“Counterfactual Dependence and Time’s Arrow” and “Causation as Influence” are under consideration
in this essay. The first essay “Counterfactual Dependence and Time’s Arrow” will be used to
demonstrate Lewis’ original counterfactual analysis. After criticism towards this original theory, the
second essay “Causation as Influence” shows Lewis’ revisions to his argument. It is from these two
essays that one should have a comprehensive understanding of counterfactual theories of causation, at
least as Lewis sees it, only to be followed by criticism from Michael Strevens’ essay “Against Lewis’ New
Theory of Causation.”
To better understand Lewis’ theory, it is best to have an initial understanding of the
counterfactuals that Lewis employs. A counterfactual is in regards to a proposition including event A and
event B where B follows from A that if A were (or had been) the case, B would be (or have been) the
case. It is important to understand that event A and event B are separate events. Still in Lewis’
counterfactual theory, there exists a causal dependence between the two events. Causal dependence is
a critical point in Lewis’ theory and consists of a set of qualifying conditions. First in order for there to be
causal dependence is that causal dependence occurs between events. The second condition for causal
dependence is that the two events be distinct from each other. What this means is that these two
events cannot be related in a sense that they are identical, overlap, or imply the other. Lastly for causal
dependence, Lewis claims that it should not include what he calls backtracking counterfactuals which
hold the past to be fixed in time. It is the counterfactual and the causal dependence upon which Lewis’
theory rests.
The causal dependence that is critical to Lewis’ theory when taken into consideration requires
the understanding of time. Lewis makes the point to show the asymmetry of time. This is especially
apparent in “Counter Dependence and Time’s Arrow.” The asymmetry of time is that the past is fixed in
place whereas the future seems to be ambiguous and open to possibility. This seems to be a matter of
fact that is common sense. Despite this seemingly common knowledge, Lewis is careful to explain this as
it is not a fact that is known in and of itself or a priori. It is only from empirical knowledge that we come
to know the asymmetry. Lewis explains it that “The way the future is depends counterfactually on the
way the present is. If the present were different, the future would be different; and there are
counterfactual conditionals, many of them as unquestionably true as counterfactuals ever get, that tell
us a good deal about how the future would be different if the present were different in various ways.
Likewise the present depends counterfactually on the past, and in general the way things are later
depends on the way things were earlier. Not so in reverse” (Lewis 455). What this quote demonstrates is
better known as temporal asymmetry. It is because of this asymmetry in time that Lewis claims that
causal dependence, and therefore causation, is asymmetrical as well. This is backed primarily by Lewis’
claim that there is asymmetry of overdetermination. Asymmetry of overdetermination is essentially that
earlier events determine later events but that this does not happen in reverse.
Another asymmetry that Lewis presents is that considering the asymmetry of miracles. Consider
the example of Nixon having possession of button that releases nuclear weapons, resulting in a nuclear
holocaust. It is important to note that Lewis wants to consider the closest actual world. This is important
as we approach the situation closer. The two possible worlds are that Nixon does not press the button
and that Nixon presses the button. The one where he presses the button results in a nuclear holocaust
which is a world far different from our own. Suppose now that Nixon presses the button and the button
malfunctions in a way that it prevents a nuclear holocaust. What this shows is that the malfunctioning
case is more similar the real world than is the one where Nixon pushes the button. This demonstrates
that in order for the world to be similar to the real world is much more than the alternative world. As
Lewis puts it that “Divergence from a world such as w0 is easier than perfect convergence to it” (Lewis
475). Since divergence is easier than convergence, Lewis is able to explain a fact important to causal
dependence since “The asymmetry of miracles, and hence of counterfactual dependence, rests on a
feature of worlds like w0 which very simple words cannot share” (Lewis 475).
A problem that Lewis, as well as older counterfactual theories, faces is that of preemption.
Preemption is an attempt to dismantle the causal dependence that Lewis is arguing for. Preemption
takes two different forms. There is early preemption and late preemption. For right now we shall only
consider early preemption in the face of early counterfactual theories and Lewis’ rebuttal. An example
of early preemption would be that of two assassins attempting to kill a primer minister. Event B would
be that the first assassin throws a knife at the prime minister’s head and that event C is another assassin
decapitating the prime minister. Event D where blood squirts from his neck follows from event B and so
event E is the result of event C. Yet this is not necessarily true for D is a guarantee that event E
happened. This seems to pose a problem for simple counterfactual theories. For after all D did cause E,
they both occurred, C and E are wholly distinct; however, E does not counterfactually depend on C at all.
Instead it is counterfactually dependent on D. This seems to stump original counterfactual theories, yet
Lewis has a rebuttal. In addition to the four points found in original counterfactual theories, Lewis adds
that in order for C to cause E there must exists a causal chain from C to E. What he means by chain is
that each event counterfactually depends on the previous event. How this relates to the example of
early preemption is as follows. Event E is not counterfactually dependent on C because if event C had
not happened event E would in virtue of event B. Lewis solves this problem though that there exist a
causal chain between event E and event C based on counterfactual dependence. It is from this transitive
chain that we see that event C causes event E and therefore Lewis has overcome early preemption.
Looking back, there is a general understanding of Lewis’ original theory. His counterfactual
theory relies on causal dependence which as of now is rather sturdy. In addition to causal dependence,
Lewis has provided a logical backing that causal dependence is asymmetrical because there is no a priori
evidence to prove such asymmetry. Lewis also includes the transitive causal chain as a way of
responding to problems brought on by early preemption. It is from this original composition of Lewis
that there are evident advantages to his theory.
Still although positive qualities exist in Lewis’ theory, there are still flaws in his original thesis.
One of the issues with Lewis’ theory is that it is context sensitive. By context sensitive, it means that
Lewis’ causation only pinpoints one cause to an effect in all situations. This absoluteness cannot be true
as Lewis’ theory implies. Consider the case where a camper lights a fire, where the fire is then blown by
a gust of wind such that it catches to the rest of the forest and the forest burns down. It seems
commonsense to the reader and for Lewis that the cause of the fire was the camper lighting the match.
However it is also possible to consider that the oxygen present in the environment was also the cause
for the spreading of the fire. Lewis would say that the oxygen present is not a cause but merely a
condition for the fire. Yet if we were to take the spread of a fire in a laboratory, where oxygen is meant
to be excluded, then it seems as if oxygen would be the cause of the fire spreading. This demonstrates
that Lewis’ theory does not account for different causes that result in a certain effect. Still, Lewis would
argue that he is interested in the broad notion of cause in such a way that the camper lighting a fire is
still responsible for the fire and the oxygen present is merely an additional condition to fire.
Context aside, Lewis’ theory is still under scrutiny when under the consideration of temporal
asymmetry. Temporal asymmetry rests under the idea that the past is fixed and that the future is
undetermined. Essentially it is that the past determines the future. However the laws of
thermodynamics are symmetrical in time. Although it is very rare possibility, one can imagine a cooked
egg returning to its raw state and hopping back into the shell. It is with this that Lewis’ temporal
asymmetry seems to not be as strong.
Another issue with Lewis is over transitivity where it can be claimed that a certain event causes
another event even though they are not directly related. This would be in such a case where event A
causes event B and that event B causes event C. This in turn deduces that A causes C. This type of
thinking runs into issue with Lewis’ theory. Take the example of a hiker in the woods. The hiker is
walking along the trail when suddenly a boulder is dislodged and comes tumbling towards the hiker’s
way. The hiker seeing this tumbling boulder, ducks preventing being hit by the boulder, and then
considers to walk on the path. It is from this example of a causal chain that the boulder not only causes
the hiker to stop and duck, but to also continue his stride. This proves to show some difficulty in
transitivity for Lewis’ theory.
The issue of transitivity is a difficult one to answer. This is partly in fact that it is associated with
the preemption, which Lewis’ theory also has difficulty dealing with. It was earlier mentioned during the
example of the assassins and the prime minister that Lewis’ original theory was able to side step such an
objection. This is only possible under early preemption. There is early preemption and late preemption.
Early preemption is when the preempted alternative is cut short in a process before the process reaches
completion. Late preemption is when the main process has gone through completion and brought about
the effect. Assume that we have two people, Billy and Suzy. Both are throwing rocks at a bottle. Event B
is that Billy throws a rock at the bottle. Event C is that Suzy throws a rock at the bottle and is slightly
ahead of Billy, and as a result event D where the bottle breaks. The example results with the bottle
being broken regardless of Suzy. Even if she threw later or earlier, the bottle would have been broken.
This shows that the shattering of the bottle is not counterfactually based on Suzy. This is an issue for
Lewis for early preemption had the effect depend on a middle event that involves the action of the
cutter. With late preemption, the focus is pushed to the last event. Because of this effect on the last
event, Lewis is unable to side step the issue as he was with early preemption. Thus this is a problem for
Lewis’ original theory.
Context sensitivity, temporal asymmetry, and transitivity are minor criticisms of Lewis’ original
counterfactual theory. It is the issue of late preemption and the trumping argument which provide the
most difficulty for Lewis. Late preemption is the issue where the ending event is of no concern for there
are multiple causes possible for the effect. Still there is trumping, which uses simultaneous causes to
result in the same effect. Consider the example of a sergeant and a general commanding a group of
troops. The general has authority over the sergeant and so his word has more authority. Suppose then
that at event B that the sergeant shouts “Advance” and at that same time that event C happens where
the general shouts “Advance.” The soldiers in turn hear the general’s command at event D and so results
in the soldiers advancing at event E. Although the troops are meant to obey the superior officer, it is not
necessarily true that C caused E as E is not counterfactually dependent on C. This example is not
counterfactually dependent because E would have happened because of the presence of event B. One
possible objection would be to say had Billy’s rock or perhaps Suzy’s rock shattering the bottle at a
different time would be a different shattering. This is not a sound objection as just because an event
occurs at a slightly different time does not mean that it is a different event.
It is from the problems brought on by late preemption and trumping, that Lewis’ original theory
no longer holds as being sound. It is from here that we shall turn to his recent theory explained partially
by his essay “Causation as Influence.” Lewis returns to the issue mentioned at the end of the paragraph
above regarding the time of event. Contrary to what is said, he in fact believes that time is a factor. The
evidence that Lewis brings to the argument is that “Without the hanging that allegedly caused the death
of Ned Kelly, for instance, he would sooner or later have died anyway, but he would have died a
different death and the event that actually was Kelly’s death would have never occurred” (Lewis 185).
What Lewis is demonstrating is that events are fragile. Lewis extends his points of the fragility of events
to include that events are contingent on how, when, and whether. This leads Lewis to conclude that for
every event C causing event E that there is a series of possible C events as there are possible E events.
Returning to the issue of Suzy and Billy Lewis is able to respond that “Suzy’s throw is much more of a
cause of the bottle’s shattering than Billy’s. Even if the throws are so much alike that removing Suzy’s
throw altogether, it is still true that altering Suzy’s throw slightly while holding Billy’s fixed would make
a lot of difference to the shattering, but altering Billy’s throw slightly while holding Suzy’s fixed would
not” (Lewis 191). This same kind of reasoning can be applied to the trumping example as well. Changing
the shouting of the major’s command while keeping the sergeants fixed would make a difference
whereas changing the sergeants command and keeping the major’s would do little to nothing at all. It
seems from “Causation as Influence” that Lewis has revised his original theory to combat some old
problems.
Looking at Lewis’ theory though shows that there are some modifications. One of the more
notable ones is the action he takes towards causal dependence and transitivity. Lewis asks “Is it still
necessary to take the ancestral, now that our definition of causal dependence has evolved from simple
whether-whether dependence to a pattern of influence? Does our improved definition of dependence
allow us just to identify causation with causal dependence? No. Influence is not invariably transitive”
(Lewis 191). It seems as if Lewis is straying away from a transitive property. Lewis shows in his essay how
different events can be the result of different causes or that the same cause can affect different events.
With alterations and the fragility of events, it naturally follows the contemplation of events which are
absent from a causal chain. Lewis mentions the existence of absences and how they affect causation.
The fact that there is an absence of nerve gas is that we are able to live and breathe the air. Lewis does
not want readers to get carried away with what he means by absence for “Absences are not events.
They are not anything: where an absence is, there is nothing relevant there at all. Absences are bogus
entities. Yet the proposition that an absence occurs is not bogus” (Lewis 195).
Having looked at Lewis’ original theory followed by his revisions in “Causation as Influence”
there seems to be a well back support for counterfactual theories. As of now, Lewis has what appears to
be successfully rebutted against major objections towards his theory. We will turn now to a recent
objection posed by Michael Strevens. Strevens takes issue with the main component of Lewis new
theory being that involving alterations. Strevens refers to these alterations as a concrete event. Strevens
takes issue with the idea of fragility as “Had the jar shattered a moment later, or had it broken into a
slightly different number of shards of glass, this concrete event would have never occurred” (Strevens
2). This seems to be a pickier interpretation of Lewis’ an argument. Strevens then simplifies Lewis’
argument to the where if C is the cause of E then if C would not have occurred then E would not have
occurred. This summary of Lewis’ theory comes off as being a bit of an over simplification of Lewis’
argument. This simplification is even simpler than his “Counterfactual Dependence and Time’s Arrow”
argument. Furthermore, this view does not reflect his later “Causation as Influence.” Strevens poses a
counterexample where Sylvia and Bruno throw rocks. Sylvia throws a right angle from a jar while Bruno
throws a rock directly at the jar in such a way that Sylvia’s rock deflects Bruno’s rock and in turn hits the
jar. Strevens claims that this shows that “Where Lewis goes wrong is in equating the causal relation
between events and the causal influence relation between their concrete realizers” (Strevens 10). What
this means is that Strevens is against causal claims where event C is the cause of event E is now riddled
with a multitude of causes that each take part in making event E. Strevens then moves on to his issue
with causal influence by its own. Strevens explains that his counterexample shows dependence on both
Sylvia and Bruno’s rock throw and that there is not a possible alternative. This appears to side with Lewis
more than against it as it is sensitive to the how, when, and whether conditions that are important to
Lewis. From my interpretation, Strevens seems to draw a lot of points that don’t promote his argument
and ultimately weaken his original claims including his counterexample.
Having considered both of Lewis’ positions and a counter example provided by Strevens it
seems as if we have a well-rounded understanding of counterfactual theories of causation. Obviously
traditional views such as E as a result of C only if C had not occurred then E would not have occurred will
not stand under such scrutiny. Lewis’ original thesis, although slightly better has proven to not
withstand problems such as trumping and late preemption. It is Lewis’ revised thesis that I find most
convincing. His introduction to alternatives provides a sound explanation for why certain events have to
happen for a certain how, when, and whether. Although he may claim that these do not have to be
exact occurrences, I find this to be false. This may sound ridiculous to claim that if someone was born 30
seconds earlier that it would be a different birth. This may be arguable and even criticized by people
such as Strevens. Still, if one is to understand causation, I feel as if one must be exact when describing
events and how they occur with time and space. I find Strevens’ article to be a mislabeling Lewis’
argument and therefore will withhold any possible merits it may offer. After working through the
following three essays and comprising an understanding, I understand why Lewis is the face of
counterfactual theories of causation.
Works Cited
Lewis, David. “Counterfactual Dependence and Time’s Arrow.”Nous. Volume 13. Number 4. Special
Issues on Counterfactuals and Laws. Wiley. November 1979. Pages 455-476. April 2013
Lewis, David. “Causation as Influence.” The Journal of Philosophy. Volume 97. Number 4. April 2000.
Pages 182-197. April 2013.
Strevens, Michael. “Against Lewis’s New Theory of Causation: A Story with Three Morals.” Pacific
Philosophical Quarterly. Volume 84. Number 4. September 2003. Pages 398-412. April 2013