3. Thematic Kinships Vis-à-vis Causal Connections

Now we can turn to the following pivotal question: To what extent, if any, do mere thematic kinships bespeak causal connections? As I shall illustrate presently, thematic kinships are not only of various sorts, but are also encountered in varying degrees, ranging from very high to very tenuous. Yet it will be crucial to appreciate the following impending moral: Even when the thematic kinship is indeed of very high degree, it does not itself license the inference of a causal linkage between such thematically kindred events.

Thus, let us now consider just a few examples from some fields of inquiry outside psychoanalysis in their bearing on the inferability of causal relatedness among events or states that feature diverse sorts of thematic affinities or isomorphisms. These examples will serve as salutary preparation for appraising Freud's etiologic inferences from thematic affinity as well as of the objections of some of his hermeneutic critics.

1. A tourist looking at an otherwise desolate beach notes that the sand reveals a string of configurations exhibiting the same shapes as the left and right shoes worn by humans. In short, the tourist observes a geometric isomorphism–or "thematic affinity" of shape–between the sand configurations and the shoes. He will then draw the causal inference that a person wearing shoes had actually walked on the beach, and had thereby produced the sandy shapes that we call "footprints." But just what licenses this causal inference?

The lesson of this example, I claim, is as follows: The striking geometric kinship between the two shapes does not itself suffice to license the tourist's inference that the foot-like configurations were, in fact, caused (or produced) by the impact of human feet on the beach. To draw the inference, the tourist avails himself of a crucial piece of additional information that cannot be known a priori from the mere geometrical kinship: Foot-like beach formations in the sand never or hardly ever result from the mere collocation of sand particles under the action of air, such as some gust of wind. Indeed, the additional evidence is that, with overwhelming probability, in the class of beaches, the incursion of a pedestrian into the beach makes the difference between the absence and presence of the foot-like beach formations.

In short, going beyond the mere sameness of shape, the tourist relies on essential empirical evidence for the overwhelming probability that the sameness of shape was not a matter of mere chance, when he or she draws the causal inference that the sandy simulacrum of a human foot is, in fact, actually the trace or mark left by a human foot, and thus a bona fide footprint (cf. Grünbaum, 1984, p. 63). Let me just remark that one reviewer of my 1984 book The Foundations of Psychoanalysis: A Philosophical Critique incomprehendingly ridiculed this telling epistemological point as pedantic talk about the word "footprint"!

2. Two significantly different dreams will now serve to show that reliance on mere thematic connections to draw causal inferences is a snare and a delusion. This moral will, of course, also apply to Freud's particular dream theory as a special case. But for simplicity, I shall deliberately not make any psychoanalytic assumptions in dealing with my two dream specimens. In the first, though not in the second, we shall indeed have license to draw the causal inference that the manifest dream content was shaped thematically by a salient component of the waking experience on the day before.

But my point in giving this first dream example will be to contrast it with a second, which is of another kind: In the latter, it is demonstrably fallacious to invoke a thematic connection between the waking experience of the previous day and the manifest dream content as a basis for inferring a causal linkage between them.

Let me now turn to the first of the two dream examples. Note that this specimen is hypothetical, since I don't know of anyone who actually had the putative dream. I devised this first example, because it features a bona fide case of both causal relevance and thematic affinity. The dreamer is a woman, whom I shall name Agnes. The night after her first visit to Frank Lloyd Wright's famous house "Falling Water" (in Ohiopyle, Pennsylvania), she dreamt about a house just like it, down to many of the fine details of its interior appointments. It is important that Agnes had never heard of Falling Water until the day of her visit, let alone seen a picture or description of it. It is also crucial that the very first time that Agnes's manifest dream content ever contained such a simulacrum was the night after her daytime visit to that Frank Lloyd Wright house.

Without these additional facts, the strong thematic affinity between Falling Water and the dream content would not itself legitimate the inference that Agnes's visit to Falling Water was causally relevant to the presence of a simulacrum of that mansion in her dream during the night after the visit. In short, Agnes's visit made a difference to her having that dream. And the relation of making a difference is a crucial ingredient of the relation of causal relevance. Thus, in this case of thematic affinity, there is warrant for the causal inference, because of the availability of appropriate additional facts. But now consider a related example of thematic affinity with the opposite inferential moral.

3. Assume that last night, my manifest dream content included the image of a house. In my urban life, I routinely see and inhabit houses daily. Thus, my impressions on the day before this dream featured visual and tactile impressions of at least one dwelling. Indeed, over the years, on the day before a dream, my waking experience always includes seeing some domicile or other, regardless of whether the ensuing manifest dream content then features the image of a house or not! In this case, I claim, seeing a house on the day before does not make any difference to dreaming about a house the night after, because I see houses during the day before whether I then dream about them or not.

Evidently, in the latter dream example, when a house is an element of the manifest dream, the presence of a house theme in the prior day's waking experience does not meet the key requirement for being causally relevant to the presence of a house-image in the dream. To put it more precisely, my seeing a house on-the-day-before-a-dream does not divide the class of my-day's-waking-experiences-on-the-prior-days into two subclasses, such that the probabilities (or frequencies) of the appearance of a house in the next dream differ as between the two subclasses. On the other hand, in Agnes's life, just such a division into subclasses by the experience of seeing the Falling Water house does occur, with ensuing different probabilities of dreaming about that house.

We see that there is a sharp contrast between my two dream examples: If a house-image occurred in my dream last night, it is a mistake to attribute that image causally to my having seen one or more houses yesterday, although there is undeniably thematic affinity between them. Thus, it is eminently reasonable to conclude that, despite their thematic affinity, the dual presence of the house theme both in yesterday's daytime experience and in last night's dream was a happenstance, rather than a case of causal linkage between them.

The major significance of the second dream example for psychoanalytic causal inferences turns out to lie in the following fact: As illustrated by the rat theme in the case of Freud's Rat Man, in the typical psychoanalytic etiologic inferences, the thematic affinity is no greater, and often even weaker, than in the second house dream case. In fact, it is fairly easy to weave thematic affinities between almost any two experiences, and the vivid imaginations of psychoanalysts enable them to have a field-day with doing so.

My account of the second dream example may be greeted by disbelief, because it might be thought that I have overlooked an important pertinent fact. We might never have dreamt about any house at all, unless we had seen one at some time or other in our lives. Far from having overlooked this necessary condition for house-dreams, I shall now explain why this mere necessary condition is demonstrably not tantamount to the causal relevance of my house-seeing-experience-on-the-day-before-a-dream to my dreaming-about-a-house-the-night-after.

This lack of causal relevance of a mere necessary condition can be seen at once from the following example: Breathing is a necessary condition for being paranoid, but breathing is not causally relevant to being paranoid. If the wife of a paranoiac were to ask a psychiatrist why her husband is paranoid, the doctor would surely not answer, "Because he is a breather." Let us see why not.

Breathing is a necessary condition for being paranoid, because a person has to breathe to be alive, and in turn has to be alive to be paranoid. A dead paranoiac is surely not paranoid. What matters is that all living non-paranoiacs breathe no less than all paranoiacs do! Thus, breathing does not affect the incidence of paranoia within the class of living humans, because it does not even divide this class into two subclasses. A fortiori, it does not divide it into two subclasses in which the incidence of paranoia is different. Though breathing is thus a necessary condition for paranoia, it is surely not causally relevant–within the class of living persons–to becoming paranoid. In other words, although breathing does make a difference to being alive or dead, it makes no difference to being paranoid rather than non-paranoid.

Thus, in the context of dreams as well, a state of type X may be a necessary condition for the occurrence of some other sort of state Y in a given reference class, although X is not causally relevant to Y within that reference class. As I have illustrated, if X is to be causally relevant to Y in a reference class C, X must partition C into two subclasses in which the probabilities or incidences of Y are different from one another. But let me add parenthetically for the case of house-dreams: In the different reference class of all humans–which includes people who may never get to see a "house"–seeing-a-house may indeed be at least statistically relevant to dreaming about it. But even that would not necessarily bespeak causal relevance.

It is true that, in the case of the second house dream now at issue, which was dreamt by me rather than Agnes, the thematic affinity between the-day's-waking-experience-of-some-house and the next dream about-a-house is clearly much weaker than in the Agnes and Falling Water example. But there is a telling counterexample to the supposition that every case of high thematic affinity also turns out to qualify as an instance of causal relevance: Consider a woman who sees her husband every day of their married life, and whose dreams over the years occasionally feature him undistortedly. Then precisely her inseparability from her husband in waking life shows that her having-been-with-him-as-well-on-the-very-days-before-dreaming-about-him is not causally relevant to the production of that thematic dream content the night after!

Besides, recall my earlier caveat that even in the example of the footprint, which features very strong thematic affinity, the mere presence of a very high degree of such kinship was quite insufficient to validate the causal linkage.

Hence it would be a momentous error to believe that causal inferability goes hand-in-hand with a very high degree of thematic kinship.

For brevity, I add an instance from evolutionary biology that tells against drawing causal inferences from thematic kinships. As Elliott Sober (1987; 1988) has pointed out: When species match with respect to what are called ancestral characteristics–which is a certain kind of thematic affinity–this similarity is not cogent evidence for the causal inference that they share a common descent. Yet, in the context of other information, a match in regard to "derived" characteristics–which is another sort of thematic affinity–does qualify as evidence of a shared genealogy.

We are now ready to appraise Freud's own causal inferences from thematic connections. As a corollary, we can reach an important verdict on the objections that Freud's hermeneutic critics leveled against him.