“The Incommensurability Problem and The Fermi Paradox”
by Eric Davis
astrophysicist at the National Institute for Discovery Science

I would like to focus on an important, very key comment made in the second paragraph of Fermi’s Paradox and the Preparation for Contact Hypothesis. I refer in particular to the passage: “…a second common objection to the UFO phenomenon by scientists: that the observations indicate such utterly nonsensical, bizarre behaviour that it just could not possibly be real. Intelligent visitors just would not pull such disreputable antics as have been reported.”

This so-called second objection can be addressed and understood if members of the scientific community would look at the UFO problem in terms of the Incommensurability Problem and semiotics (1,2). There has been recent news about new search paradigms and techniques being developed within the Search for Extraterrestrial Intelligence (SETI) programs. Briefly, these efforts are the COSETI effort for detection of coherent optical ETI signals, SETA and SETV (Search for Extraterrestrial Artifacts and Search for Extraterrestrial Visitation), and the recently announced Australian SETI effort to look for holographic images sent by ETs. SETV, as described by Stride (3,4), looks for near-Earth ETI probes but also overlaps with monitoring of UFOs. This is demonstrating a serious paradigm shift away from the traditional radio SETI approach of Frank Drake et al. I believe this is occurring because many SETI workers now realize that we cannot be so presumptuous as to assume that ET cultures, having a cognitive mismatch with us or having the Incommensurability Problem, will behave as we do and develop only radio-based interstellar communications technology. The view that ETs and humans may have such divergent ways of conceptualizing the world that there can be no mutual understanding is referred to as the Incommensurability Problem. The cognitive mismatch or Incommensurability Problem between human and ET cultures will guarantee that many ET cultures will develop communication techniques other than radio. There are likely to be signals in the form of other physical manifestations for which we have not yet devised technical communications scenarios, such as holographic images, modulated neutrinos, gamma ray bursters, wormhole modulated (background) starlight caustics, signals generated by gravitational lensing techniques, X-rays, quantum teleported signals, or some quantum field theoretic effect/manifestation, etc. This list is not all-inclusive.

The Incommensurability Problem

At the core of the Incommensurability Problem is the view that no intelligent species can understand reality without making certain methodological choices, and that these choices may vary from civilization to civilization (2). If ETs/UFOs have different biologies and live in considerably different environments than humans, they may well have different goals for their science and they could have radically different criteria for evaluating the success of their science. Their explanatory mechanisms, their predictive concerns, their modes of control over nature might all be very different, and their means of formulating models of reality might differ drastically from ours (5).

In this regard, there is one additional feature that needs to be mentioned in support of alternative SETI paradigms. The CETI (C = communication with) and SETI emphasis on pictorial images/messages is predicated on the assumption that ETs have sight like humans. I argue that this emphasis is not so much a reflection of the primacy of vision in humans, but rather a reflection of the philosophical assumptions about the proper means of gaining knowledge.

Michel Foucault asserts that human reliance on science is based on studying visible characteristics of objects (6). This belief — that true knowledge must be acquired from sight — originated in the 17th century. This emphasis on sight as the main sensory modality for gaining knowledge led to eliminating the other senses as potentially valuable sources of scientific information.

Without even raising the question of whether ETs/UFOs can “see”, we may be wise not to overestimate the importance of pictorial representations for them. This goes the same for ET/UFO transmissions to us. We can see and gain knowledge by sight, but ET/UFO signals potentially bombarding the Earth now may be misunderstood or will go undetected because we are not employing paradigms involving our other senses (such as consciousness) that may correspond to those of the ETs/UFOs who evolved in different environments where sight does not exist or is least important for gaining knowledge. Many examples of this are found in interactions between humans from different cultures (7).

Because we cannot be certain of the nature of ET/UFO recipients when sending our deliberate messages and they cannot be certain of our nature when sending us their messages a priori, it may prove difficult to construct pictures that will be unambiguous. To some extent, ET/UFO viewers of our pictograms may project characteristics from their own species-specific experiences onto our messages, and we will certainly project our own species-specific experiences onto their messages. The former may be the cause for the lack of detected ET signals (save for those 100+ radio and optical signals which were not false positives but also not repeated by their source) while the latter could surely be the cause of the UFO phenomenon.


SETI Institute psychologist, Doug Vakoch, has pointed out something very useful called Semiotics, a general theory of signs (1): in which a sign is something that represents something else, the signified (for example the words “the coin” might represent the object you hold in your hand). In interstellar messages, in terms of classical information theory, there is no innate relationship between the form of the message and the content borne by the message. Once the information of the message is decided upon, an efficient means of encoding must be sought. In this approach, there is a purely arbitrary connection between content and form of the message. Semiotic-based messages have a wider range of possibilities for relating form and content.

Semioticians categorize signs according to the ways that the sign and signified are related to one another. In the association between the sign “the coin” and its signified object, this relationship is purely arbitrary. The sign for this object could have well been “the poofhoffer”. This is a purely conventional association. In semiotics, when the association between sign and signified is completely arbitrary, the sign is referred to as a symbol. With symbols, there is no intrinsic connection between the form of expression (the sign) and the content that is expressed (the signified).

There are alternatives to the arbitrary connection between sign and signified that is seen in symbols. One alternative is the icon. This is a sign that bears a physical resemblance to the signified. With icons, the form of the message reflects its contents. For example, the profile of the man on a modern American quarter is an icon for a specific man who was the first President of the United States. We can also represent the same man with the symbol “George Washington.” In the former case, the image of Washington is an icon because it physically resembles the signified. Icons can also be used when the signified is less concrete. For example, the scales-of-justice icon represents the concept of justice because there is similarity between the sign (scales that balance two weights) and the signified (concept of justice, which involves a balance between transgression and punishment).

It is also helpful to realize that icons are not specific to the visual sensory modality. It is possible to have a sign that physically resembles the signified in a nonvisual way. For example, the fly Spilomyia hamifera beats its wings at a frequency very close to the wing-beat frequency of the dangerous wasp Dolichovespula arenaria. As a result, when one of these flies is in the vicinity of a group of these wasps, the fly gains some immunity from attack by insect-eating birds. The fly’s mimicry of the wasps occurs within the auditory modality; it is not attacked by would-be predators because it sounds like the wasps. In short, the fly’s defense strategy is based on producing an auditory icon, in which the fly’s wing-beating (the sign) physically resembles the wing-beat of the wasps (the signified) (1,2).

Icons could function in any sensory modality. Given that we are not sure which sensory modality will be primary for ETs/UFOs, a sign for communication that is not reliant on any particular sensory modality would be preferable. In SETI/CETI, electromagnetic radiation is used as an iconic representation, allowing a direct communication of concepts (Earth chemistry, solar system organization, human DNA, math, geometry, etc.) without encoding the message into a format specific to a particular sensory modality. In using icons, the message’s recipients are pointed directly toward the phenomena of interest, and not toward our models of these phenomena.

From a more complete perspective, things are not so simple. In reality, the sign and the signified are in a triadic relationship between the sign, the signified, and the interpreter of the relationship between the sign and the signified. Thus, the similarity that exists between an icon and its referent does not exist independently of the intelligence perceiving this similarity. Although in iconicity there is a natural connection between the sign and the signified, this connection cannot exist without intelligence to observe the connection.

Ultimately, the problem of iconicity is that similarity is in the eye of the beholder. And because we do not know what ETs will be like, we cannot be sure that what to us seems an obvious similarity will be seen as such by intelligence with a different biology, culture, and history, or even a different dimensionality. (Imagine the classical theoretical example of three-dimensional beings passing through a two-dimensional world. It is also possible to consider interactions between intelligences involving the same number, n, of dimensions, but different characteristics between the n dimensions.) Thus, recongnition and judgement of similarity is not purely objective, but is influenced by a variety of factors that impact conventions of interpretation.

The UFO Problem

Vallee (8-11) has concluded that the UFO phenomenon is consistent with a technology centered on craft using a very revolutionary propulsion system, which possesses physical, anti-physical, psychic, social/psychology, physiological and cultural dimensions (see, reference 9 for further detail). The phenomenon is the product of a technology in the sense that it is a real, physical, material object. The UFO phenomena behaves like an intelligent control system, impacting or modifying the social psychology and mythology or mystical character of its witnesses/victims, and is “absurd” in its interaction (abductions, close encounters, abduction-related medical experiments on witnesses, craft that change technical appearance to match the technical advancement of our culture, bizarre beings, similarity of overall phenomenon with historical/legendary phenomenon, etc.) with human society (8,10).

I submit that this absurdity of UFOs is not absurd (nonsensical, bizarre, ill-behaved)! This “absurdity” is merely a reflection of the cognitive mismatch or the Incommensurability Problem that is likely to exist between humans and the UFOs.

In this particular case, the UFOs are sending the message and we are the recipients. The message(s) they are sending to us are icons: icons fashioned by the phenomenon and sent to us via some yet to be determined sensory modality. The differences between our respective cultures, biologies, sensory modalities, histories, dimensional existence, physical evolution, models of nature and science, etc. are directly responsible for our total lack of understanding of the UFO phenomenon and what their message is. We cannot see what UFOs believe to be (iconical) similarities in the message that is intended for us. These stated differences directly impact our conventions of interpretation in such a way as to impair our recognition of the “similarity” between the sign and the signified contained within the icons of the UFO message, further impairing our ability to “see and understand” their message.

The difference between the sensory modalities of UFO phenomena and humans is responsible for our inability to properly detect the UFO message (icons) and correspond with them intelligently, or in their view, they are unable to correspond intelligently with us. This difference may also prevent us from correctly interpreting what their icons are if we do in fact recognize them. In this regard, recall that we will project our own species-specific experiences onto their icons (messages) thus manifesting the appearance of “absurdity” during the human-UFO interaction. UFO abduction cases could exemplify this such that the “absurd” activities (or scenes) concurrent with abduction events could merely be the iconical defense mechanism deployed by the UFO to protect itself from the victim/subject much like the way Spilomyia hamifera protects itself from insect eating birds by mimicry.

Kuiper (12) and Freitas (13) suggest that ETI probes visiting Earth would find it necessary to hide themselves from our detection mechanisms until they have assessed our technological level or potential threat and hazards. They would employ an adaptive multi-level risk program to avoid danger. Low observable stealth such as simple camouflage through mimicry, which works well in nature, may be the technique of choice used by visiting ETI-probes/UFOs already experienced in surveillance (3). Examples of mimicry techniques are ETI-probes/UFOs entering the atmosphere with either the look or trajectory of a meteor or hidden within a meteor shower, behaving like dark meteors without the associated optical signature, hiding within an artificial or natural cloud, behaving as pseudostars sitting stationary over certain regions, or mimicking man-made aircraft’s aggregate features (3), including perhaps the mysterious unmarked black helicopters (why should a shape-shifting UFO not be able to mimic a contemporary aircraft). Another possibility is mimicry techniques employed for the manipulation of human consciousness to induce the various manifestations of “absurd” interactions or scenery associated with the UFO encounter. This in combination with the mimicry of man-made aircraft and helicopters aggregate features was prominent in the Cash-Landrum UFO case.

The current ETI Hypothesis for UFOs is not strange enough to explain the facts of the phenomenon. However, there is no experiment that can distinguish between phenomena manifested by visiting interstellar (arbitrarily advanced) ETI and UFOs. In either case, the technology exploited by such intelligences would appear to the present human race as being indistinguishable from magic and appear nonsensical, bizarre and ill-behaved (or absurd).

  1. Vakoch, D. A., SETI Institute, private communication, 1999.

  2. Vakoch, D. A., “Constructing messages to extraterrestrials: An exosemiotic approach”, Paper IAA-95-IAA.9.2.05 presented at the SETI: Interdisciplinary Aspects Review Meeting, 46th International Astronautical Congress in Oslo, Norway, 1995.

  3. Stride, S. L., “SETV – The Search for Extraterrestrial Visitation: Introduction to a Heterotic Strategy in the Search for ETI”, Journal for Scientific Exploration, submitted, Fall, 1998.

  4. S. L. Stride, “An Instrument-Based Method to Search for Extraterrestrial Interstellar Robotic Probes”, J. British Interplanetary Soc., 54:2-13, 2001.

  5. Rescher, N., “Extraterrestrial Science”, in Extraterrestrials: Science and Alien Intelligence, E. Regis Jr., ed., Cambridge Univ. Press, Cambridge, UK, 1985.

  6. Foucault, M., The Order of Things, trans. By A. Sheridan, Random House, New York, 1970, original ed., 1966.

  7. Highwater, J., The Primal Mind: Vision and Reality in Indian America, Meridian, New York, 1981.

  8. J. Vallee, The Invisible College: What a Group of Scientists Has Discovered about UFO Influence on the Human Race, E. P. Dutton, New York, 1975.

  9. J. Vallee, “The Psycho-Physical Nature of UFO Reality: A Speculative Framework”, AIAA Thesis-Antithesis Conference Proceedings, Los Angeles, 1975, pp. 19-21.

  10. J. Vallee, Dimensions: A Casebook of Alien Contact, Ballantine Books, New York, 1988.

  11. J. Vallee, Confrontations: A Scientist’s Search for Alien Contact, Ballantine Books, New York, 1990.

  12. Kuiper, T. B. H. and Morris, M., “Searching for Extraterrestrial Civilizations”, Science, 196:616-621, 1977.

  13. Freitas, R. A., “A Self-Reproducing Interstellar Probe”, J. British Interplanetary Soc., 33:251-264, 1980.