Tag: Meta

In this brief document, Tipler reviews the history and  development of the question of the plurality of worlds/extraterrestrial intelligence (ETI), from the earliest Greek thinkers through to the modern scientific era. This “meta” paper aims to justify the conclusion that the modern proliferation and acceptance of the ETI question is a consequence of developments in philosophical, theological, and empirical reasoning that been made throughout the centuries. He constructs a temporal chain linking advancements in thinking on the subject (supported by direct quotations of the primary sources), revised and modified with each new generation, that continues through to the current time. This paper is relevant to our discussion of SETI because it is one of few which attempt to comprehensively depict the status of thinking regarding the ETI question throughout history. In particular, the Greeks were separated into two schools, those who subscribed to plurality and plenitude, and those who objected; the Stoics, Pythagoreans, and Epicureans fell into the former camp, whereas the Platonists and Aristotelians the latter.  Since the cosmology of Aristotle was highly influential on the thought of the medieval scholars, the early Church Doctors concluded the concept of plurality to be antithetical to Christian theology. Not until the time of the Copernican Revolution and the emergence of the Principle of Mediocrity did the idea that other worlds could be inhabited reemerge,  and when it finally did, it did so with great force. One interesting feature of the history that this blogger did not as of yet know was the opinion held by the early Darwinists through to the modern evolutionary biologists, which turns out to be a pessimistic one on the grounds of the improbable series of millions of mutations which are requisite for the development of human-level intelligence. Tipler concludes the history at the end of the 20th century, when feelings regarding the ETI are positive due to advances in radio communication technology, theories of stellar and planetary formation and abiogenesis, and the contemporary cosmology which supported the thesis. Since this paper is not really a scientific paper in itself, but rather an exploration of the history of scientific and pre-scientific thought on the matter, it is fitting that a subsequent paper, to be written either presently or at some future point, should contain a continued account of the ETI question by way of a comprehensive treatment of SETI developments through the 21st century.

“A Brief History of the Extraterrestrial Intelligence Concept” by Frank Tipler is a meta-paper about (or more appropriately, against) SETI as a funded endeavor. The author assigns three different characteristics to the philosophy of SETI-proponents throughout time: plenitude (the belief that Earth is not a special location: in current parlance, the principle of mediocrity), infinite cosmos, and a lack of a sense of history. It is this last point that he seems to try to prove in the paper, going through the ideas of philosophers for and against SETI from Greek times onwards.

There is certainly a place for a discussion of 2000 years of theology and philosophy about whether we are the only intelligent life in the universe. We can stand on the shoulders of all of this work that has come before us, and not worry about uselessly retreading the same ideological ground. That’s a sound and fair reason to be familiar with the long literature. However, using the existence of the literature itself as a counter-argument seems unfounded and rather mean-spirited.

Of course, as one of the slandered SETI-proponents, I had a pretty strong negative reaction to the paper. I felt that the Hart (1975) paper, equally pessimistic, actually engaged the issue with quantitative calculations and a scientific basis. I know that this paper was assigned to let us see the full spectrum of arguments and beliefs about ETI, positive and negative, and for that, it certainly has value. But I strongly disagree with the line of evidence that Tipler chose.

Tipler claims that those in favor of SETI are “always willing to suspend the physics of their day.” But in his conclusion, he points out that there have been scientific advances in the previous two decades which lend credence to SETI: the nebular hypothesis, the Urey-Miller experiment, the development of radio astronomy, and the steady-state theory of the universe. And then he disregards all of these ideas before really engaging with them, ending his paper by stating that the “philosophical and theological beliefs are the main motivations for the belief in ETI”.

In addition, I would contest that going through the history this way provides both pro-SETI and anti-SETI arguments, the pro-SETI ones being played down in this particular paper. For example, the reoccurrence of the idea of ‘plenitude’ throughout history is interesting and good to be aware of… but calling it a flaw of current SETI practitioners seems a bit silly when, again and again, it’s been correct (we aren’t the center of the universe, or solar system, or galaxy, or universe…). Is that a replacement for evidence? Of course not. But if we’re engaging in a philosophical discourse, it’s a reasonable fact to bring up.

More politically, and less scientifically, the fact that SETI has been in the (European/Western/white/male*) public consciousness for so long is perhaps a reason to pursue it, instead of an argument against it. We’ve wanted to know the answers for so long, but now we have the tools to do so – does that not bring value of its own, divorced from any scientific results or merit?

Being aware of one’s biases is important, especially if you’re doing calculations that will a) later affect actual, observational work and b) can be heavily skewed by coming in with priors (looking at you, Drake Equation). Post-discussion, I am a little more accepting that there is a place for this paper. But only a little.

*someday, I would love to do a review of the history of the idea of extraterrestrial intelligence in other cultures – I’ll add it to the list!

In 1975, Hart published his paper “An Explanation for the Absence of Extraterrestrials on Earth,” where he methodically presents every well-known explanation for this (below) and then presents his own explanation: that mankind on our Earth is the first civilization in our Galaxy.

First, let me say that I appreciate this paper. I did not find any logical fallacies or leaps in an attempt to justify what he claimed. Instead, everything seemed well thought-out and matched with diction appropriate to his stance: that given the paucity of evidence and lack of other theories that sufficiently support this paucity, we should accept the last explanation (that we are the first).

As mentioned before, Hart methodically goes through possible explanations for why there are currently no creatures from other planets on Earth (he does mention that this could be wrong, but is improbable). The top explanations for this include physical explanations (space travel is infeasible), sociological explanations (the culture of the civilization does not want to visit other civilizations), temporal explanations (the civilizations will visit us but have yet to arrive because space travel takes time), and simply that others have visited us before but decided not to stay. Each of these theories is introduced, explained, and then debunked. As a spoiler alert, any explanation of why there are currently no alien species on Earth would have to hold for all civilizations that arise, and for the lifetime of these civilizations.

Space travel is in fact possible. This paper was published after the moon landing, so even at that time, Hart knew that humans could at least go to the moon. Any problems dealing with space travel can be overcome with technological advances or even just enough time and money.

Hart sufficiently (in my mind) eliminated sociological explanations completely. The unwillingness to explore or visit places (something not really seen in our society today) could be derived from culture or religion, but it is something that is most likely fluid with time; this unwillingness would be challenged over time with new generations. Even if thousands and thousands of generations of a civilization are in fact against visiting others, this outlook could not possibly be held (for forever) by every single civilization.

Temporal explanations are also dismissed quickly (dismissed as unlikely but plausible); even though space travel takes time, it would take us only 650,000 years to traverse the Galaxy. For this explanation to satisfy the fact that no alien species are currently on Earth, the first civilization with the desire and ability to travel space would have required 10 Gyr to arise AND for our civilization to arise as second about 1Myr later. Because of the unlikeliness of both of these being true, Hart dismisses this argument as  possible, but highly unlikely.

Lastly, the theory that other species did visit but are no longer here is dismissed in the same why  sociological explanations were eliminated. Although plausible for this to be true for one civilization, it is unlikely that all civilizations that visited decided to leave and never return (or died here, or died before being able to return).

Since there is no adequate explanation for why there are currently no alien species on Earth, Hart concludes that we are probably the first civilization in our Galaxy.

I personally enjoyed this paper mostly due to the lack of logical leaps and bounds. That being said, I think the conclusion is a bit pessimistic. Since we can’t really prove a negative (that there are no other civilizations) and since finding intelligent life would be amazing, we might as well keep looking!  Hart includes in this conclusion that “an extensive search for radio messages from other civilizations is probably a waste of time and money,” which I completely disagree with (I might be biased). I think there is merit to these searches beyond just looking for aliens; they lead to valuable data and technologies, and even lead to some people joining the fields of astronomy and astrobiology.

 

Arguments for or against SETI rarely invoke the theological and philosophical evolution behind such reasoning. Tipler, in his 1981 article, presents an historical approach to the concepts of extraterrestrial intelligence (ETI). The debates and arguments for or against ETI periodically reappear throughout history, albeit slightly refashioned to reflect the principles of any contemporaneous philosophical movement. Tipler introduces two related philosophies: the principle of plenitude and the plurality of worlds. The principle of plenitude surmises that what can exist must exist, such that the Universe contains all forms of existence and intelligent life must exist in elsewhere. The plurality of worlds describes the Universe as infinite, producing an indefinite number of worlds which may harbor life. Tipler then provides the historical evolution of these ideas discussing the Greco-Roman debates, the Copernican revolution, the scholasticism of the Medieval period, the Enlightened support for the plurality of worlds, and finally the scientific view of these philosophies.

Of particular interest was to see the evolution of the concept of the plurality of worlds. Prior to the Copernican revolution, the Ptolemaic Universe reigned supreme and the plurality of worlds meant an infinite number of self-contained Universes with a central Earth. Tipler mentions that despite having the physics wrong, this particular thought is akin to the modern support of ETI by the principle of mediocrity. The principle of mediocrity states that we are not special in the Universe such that, given the existence of life on Earth, life exists in other Earth-like planets in the Universe. The Christian argument against ETI was also intriguing. St. Augustine wrote that the uniqueness of Christ meant there was no other intelligent life, else they would have a separate Christ for such a world. St. Thomas Aquinas argued that God was perfect; which was inconsistent with the plurality of worlds as this would be an act in vain if similar worlds existed and an act of imperfection if dissimilar worlds existed. It was not until the nineteenth century that the plurality of worlds was used to argue for ETI and against Christianity, as seen by the excerpt from Thomas Paine’s Age of Reason.

The post-nineteenth century pervasiveness of the plurality of worlds should be viewed through a critical scientific lens. It was through the scientific understanding of the geological, biological, and chemical evolution of the Earth that the principle of plenitude was rejected. Tipler repeats the arguments of William Whewell and Alfred Wallace, which were aligned with that of evolutionary biologists in that they argued the Earth was uninhabited for most of its history and, to our knowledge, the conditions for life and natural selection are incompatible with harsh environments elsewhere. Tipler, unfortunately, does not muse over the fact that a post-Enlightened society would use the plurality of worlds to fuel the imagination and foment the idea that humans are not alone in the Universe (i.e. It Came From Outer Space or the spoof, It Came From Planet Earth). Most surprising to this blogger was that modern evolutionists argued against ETI while physicists and theologists appeared to have no issues with it. While the scientific community, with achievements such as the development of radio communication and the Miller experiment, may have cemented the belief in the plurality of worlds and the search for ETI, the larger biological and chemical considerations appeared to be ignored during the late twentieth century. Despite the support the principle of mediocrity provides ETI, it is imperative to address all scientific concerns regarding ETI. Perhaps it is no surprise that astrobiology has recently developed to as a response to the complex scientific nature of the search for ETI.