A Plea For The ETH

John Harney
Magonia 17, October 1984.

In recent years there has developed a two-pronged attack on the extraterrestrial hypothesis (ETH) as an explanation for UFO reports. These two prongs may be termed the cosmological approach and the psycho-sociological approach. We can put them together and sum them up as follows:

There are no visitors from other planets because the Earth is the only planet in this galaxy (or in the entire universe) on which intelligent life has evolved. Thus, if we want to explain the UFO reports we must study the witnesses, their psychological problems and their interactions with society.

Now it cannot seriously be doubted that the disciplines of psychology and sociology are relevant to the study of UFO reports. However, there is a danger that total commitment to this approach could lead us astray by being employed as a catch-all explanation for anything resembling a UFO report.

The psycho-sociological approach is reinforced by current theories about extraterrestrial life which generally conclude that it is so unlikely that we might as well forget about it. This set of theories, which I have termed the cosmological approach, is itself two-pronged. Various theories of biological evolution and the evolution of stars and planets are considered in an attempt to demonstrate that the evolution of life is a singular event. This is backed up by the other prong of the cosmological approach, which is a set of arguments designed to convince us that if the ETs existed they would have colonised Earth millions of years ago.

In this paper I intend to point to some apparent weaknesses in these arguments and to urge that the ETH should not hastily be abandoned.


2.1 Suitable stars and planets
Intelligent life resembling in any way that which we know here on Earth would have to have its origin on a planet which would provide an environment having certain essential properties. It seems to be generally agreed that such a planet would have to be rather similar to Earth and be orbiting a star similar to the sun.
It is estimated that there are about 200 thousand million stars in our galaxy, and Isaac Asimov (1) considers that about 75 thousand million may be considered sufficiently sun-like to nurture life on planets which may orbit them. Although there is still much uncertainty, some theoretical work suggests that planetary systems may be common. (2)

The main argument against life arising in such systems is that it is considered very unlikely that a suitable terrestrial (i.e. earth-like) planet will exist in a stable orbit which is not too near or too far away from its parent star.

2.2 Climatic stability

Life has existed continuously on Earth for about 3,000 million years. It follows from this that the Earth’s climate cannot have changed drastically in all that time. If, in any period, the mean surface temperature had strayed outside the range 0-100 degrees Celsius then life would have been extinguished. Also, if the Earth cooled until it was completely covered with ice, the situation would be irreversible, as would a runaway greenhouse effect which would be caused by excessive heating.

It has been calculated that only very small changes in the Earth’s orbit or in the output of energy from the sun are required to produce either of these effects. Thus it is considered unlikely that any planet would remain habitable for long enough for advanced life forms to evolve.

In the opinion of the Russian scientist M.I. Budyko: “It is believed that the maintenance on Earth of a mean temperature within the narrow zone necessary for life for billions of years seems to be a random event, the probability of which is very low. To a considerable extent the comparatively small changeability of the atmospheric chemical composition, whose variation could easily destroy all organisms was also random.” (3)

2.3 Improbability of the emergence of life

It is generally believed by scientists that life on Earth arose spontaneously out of non-living matter, beginning with the formation of complex organic compounds in the primeval ocean. It has often been argued that the odds against these compounds arranging themselves in such a way as to form the first living organism are so great that the existence of life on Earth must be a singular event. For example, Jacques Monod has written that: “Man at last knows that he is alone in the unfeeling immensity of the universe, out of which he emerged by chance.” (4)

2.4 Is there life on Earth?

The arguments in sections 2.1-2.3 summarise very briefly the views of those scientists who believe that intelligent life elsewhere in the universe is extremely unlikely.

stronomers think that there are unlikely to be suitable planets at the correct distances from sun-like stars. Climatologists believe that earth-like planets would inevitably be covered by ice, or be boiling hot (like Venus). Some biologists think that the emergence of life is so improbable that it is inconceivable that it could have happened more than once. Each group calculates enormous odds against conditions being favourable to life from the point of view of their own discipline. So if we take their views seriously we must multiply these odds together and arrive at a figure so enormous that we are forced to conclude that we are merely figments of our own fevered imaginations!
As the notion that we do not really exist but only imagine we do is incoherent, we can reasonably suppose that extraterrestrial life really does exist on other planets although it perhaps does not arise very often.


3.1 The galaxy should be completely colonised

The scientific opinions mentioned in section 2 cannot lightly be brushed aside, so it is reasonable to speculate that the number of planets in the galaxy on which intelligent life develops is quite small. However, it has been calculated that any beings which achieved interstellar travel could spread throughout the entire galaxy in a period which is short compared with the age of the solar system. Eric M. Jones, for example, considers 60 million years to be a reasonable estimate. (5) Some writers have used such estimates to argue that the fact that aliens have not taken over the Earth strongly suggests that we are alone in the galaxy.

3.2 Anthropomorphic assumptions

The main weakness of this kind of argument is that it is hopelessly anthropomorphic. It is surely possible to think about extraterrestrial intelligence without having to see it in terms of the Star Wars films and similar space operas. The first race of beings to spread throughout the galaxy would doubtless be aware that they could establish themselves on every habitable planet. But they would also be aware that such a policy would pre-empt the emergence of any other intelligent life forms. Once they had spread throughout the galaxy they would also be in a position to discourage any emergent space voyagers from adopting the traditional space-opera approach to any habitable or inhabited planets which they might encounter.


4.1 Naive versions of the ETH

There are several versions of the ETH and most of them are presented in such a manner in the UFO literature as to discourage any serious enquirer from pursuing the matter any further.

There is the straight anthropomorphic version which sees the ETs as being like us mentally, if not physically. These are the kinds of beings who apparently inhabit the imaginations of writers such as Keyhoe and some of the good old-fashioned American organisations. They are so familiar, from UFO literature and science fiction, that no more need be said about them here.

Then there are the aliens of the UFO cultists, which are more difficult to deal with, as one is not sure whether they are supposed to be physical entities or purely spiritual beings, like angel

4.2 Looking at the question from the ET’s point of view

It seems to me to be unreasonable to assume that beings who have travelled throughout the galaxy for millions of years would treat a newly discovered planet in the same way that we would undoubtedly be treating, say, Mars if it were found to be inhabited or habitable. They would sometimes find it necessary to control, as well as monitor, the activities of other emergent intelligences, but they would have had plenty of time to evolve methods of exquisite subtlety, so that no creature would be aware of their activities unless they decided to reveal themselves.

As a result of the persistence of UFO reports and speculation about them since 1947, a large proportion of the Earth’s population is mentally prepared for the idea of alien contact. It could be argued that the UFO phenomenon has been carefully devised by the ETs in order to prepare us for possible overt contact. It should be possible, by means of a careful study of the pattern of UFO reports, to decide whether or not such an idea should be taken seriously. This possibility has already been discussed – but probably with tongue in cheek – by Vallee. (6)

4.3 A future for the ETH?
There is a clear division between those scientists who are interested in SETI (search for extraterrestrial intelligence) and those who are interested in the study of UFO reports. The SETI scientists are apparently quite happy with the alien intelligences, provided that they remain at a safe distance. Scientists interested in the study of UFO reports tend to be more committed to the idea that they are a version of modern folklore. However, folklore is generally concerned with amazing experiences which are supposed to have happened to “a friend of a friend”, whereas UFO experiences generally happen to identified individuals.

A revival of the ETH would depend on the bringing together of SETI scientists and “serious” ufologists. A possible meeting point might be achieved by considering the ideas of Michael D. Papagiannis, (7) who has advanced the idea that interstellar visitors to the solar system might use the asteroid belt to obtain raw materials for refuelling and refurbishing their fleets. Such visitors, if they exist, would perhaps also be curious about what is happening on Earth. Further study of such ideas might provide the basis for a fruitful exchange of ideas between ufology and SETI.


If UFO reports have nothing to do with extraterrestrial intelligence, then there is no point in pursuing the subject popularly known as ufology. If some UFO reports, or UFO reports in general are manifestations of alien intelligence, then this fact will be obscured by an exclusively psycho-sociological approach. There is a chance that the revival of the ETH, in a more subtle and sophisticated form, might possibly yield interesting results.


Asimov, Isaac. Extraterrestrial Civilizations, London, Pan Books, 1981
Isaacman, Richard and Sagan, Carl. 'Computer simulations of planetary accretion dynamics: sensitivity to initial conditions', Icarus, Vol. 3, 1977, pp 510-533
Budyko, M.I. The Earth’s Climate: Past and Future, London, Academic Press, 1982
Monod, Jacques (trans. Austryn Wainhouse). Chance and Necessity: An Essay on the Natural Philosophy of Modern Biology, London, Collins
Jones, Eric M. 'Estimates of expansion time scales', in Hart, Michael and Zuckerman, Ben (eds), Extraterrestrials: Where Are They?, Pergamon Press, 1982
Vallee, Jacques. UFOs: The Psychic Solution, St Albans, Panther Books, 1982
Papagiannis, Michael D. 'Colonies in the asteroid belt, or a missing term in the Drake equation', in Hart and Zuckerman, op. cit.