and living systems, and that under suitable physical conditions the emergence of life is highly probable [given enough time]. It is the adoption of the “continuity thesis”, concerning the philosophical dimension of life-matter relationship, which has turned the origin of life into a legitimate scientific question, and which constitutes a necessary condition for any scientific research in this domain.
In essence, the continuity thesis encompasses almost all modern approaches to the origin of life (including those postulating the origin of life elsewhere and its transport to Earth via some form of panspermia— which is crucial for our discussion here). Its substance is evocatively summed up in the title of Chapter 13 of her book: “Neither by chance nor by design”. Fry persuasively argues that the continuity thesis is the only meaningful way to proceed if one wishes to remain in the scientific domain; both the “lucky accident” naturalistic account of abiogenesis and supernaturalistic design lead us into the same blind alley. In other words, Fry’s thesis offers a much needed middle way beyond the simplistic binary extreme of “life as a miracle” (as famously argued by Jacques Monod) or “life as a cosmic imperative” (his great rival and fellow Nobel laureate Christian de Duve).2 This essential epistemological point cannot be overstated.
In [3.13], I have elaborated the case for extending the continuity thesis to the origin of intelligence (or noogenesis) and other major evolutionary transitions, or “crucial steps” in overall cosmic evolution. In particular, I suggest an extended continuity thesis, which brings the reasoning of Fry to its logical conclusion, namely, that there are no unbridgeable gaps between simple life and a complex one and between complex life and an intelligent one (possibly also between biological intelligent life and a postbiological intelligent one). Whenever and wherever physical, chemical, geophysical, ecological, etc., conditions are suitable, the emergence of complex life is highly probable—and ditto for intelligent life. This is not particularly new either. John B. S. Haldane, among others, suggested that cultural evolution is an extension of biological evolution (e.g., [3.34]). Of course, he was aware of the seeming disparity of the relevant timescales; the solution is to “zoom-out” sufficiently and seek macro-trends. Hence, the Haldanian insistence on observing evolutionary phenomena “in the fullness of time”, which is followed here (cf. [3.1]). An alternative approach is to encompass all timescales into what has been called “Big History” (e.g., [3.38]).
We are witnessing a great expansion of astrobiological research since publication of Fry’s book and much of it has either explicitly or, much more often, implicitly made use of the continuity thesis. Most interesting consequences and ramifications of it have not, however, been explored in the existing literature. The same could be said for most of other issues in the epistemological and methodological groundings of astrobiology and many of its constituent fields. It is important to emphasize this key point from the outset: there is a large amount of foundational work to be done on this subject. Considering the fact that astrobiology continues to progress in big strides a full quarter century after the “Big Bang” of extrasolar planets’ discoveries in 1995, and rather modest amount of work on epistemology and methodology of astrobiology, addressing some foundational tasks seems to recede rather than getting closer. As I shall try to show, there is important philosophical input into specific research issues which will motivate expansion of further work; the contingency thesis is just a particular example of this underlying phenomenon. By necessity, the treatment here will be laconic and sketchy, while the detailed discussion will be postponed to a future study.
That said, the rest of this chapter is organized as follows. Section 3.2 discusses versions of the continuity thesis and briefly speculates on the sources of resistance it encounters in various contexts which need not be necessarily be connected with astrobiology. The concept of chronocentrism is highlighted, representing a key underlying source of confusion, bias, and short-sightedness in considering the entire astrobiological landscape. A particular interesting consequence of an extended continuity thesis, related to the concept of directed panspermia, is considered in Section 3.3. Some ramifications for both astrobiology and SETI studies, as well as the futures studies, are outlined in the concluding section.
3.2 Versions and Resistance
While the continuity thesis as a specific concept has been introduced by Fry in 2000 [3.29], the idea itself is, of course, much older.3 In a sense, it is built in the very foundation of any kind of thinking about the life elsewhere—the very question Is there life elsewhere in the universe? is unintelligible without assuming at least a conceptual continuity. Of course, if we wish our questions not to be purely intelligible but also scientific, we need to assume stronger kinds of continuity, in particular the evolutionary kind. There is a continuity in evolutionary processes which leads to increased complexity over time. While unique naturalistic events cannot, of course, be excluded, Fry cogently points out that something which has a probability of 10−100 cannot be truly repeatable in any kind of practical terms we associate with empirical science. In this sense, such extremely rare events are on the same footing as miracles in religious sense. Since the latter are beyond the realm of science and do not allow for any kind of analysis, it is highly questionable to what extent even naturalistic “lucky accidents” are part of the scientific discourse. Therefore, the continuity thesis is an affirmation of the essential aspects of the scientific method, naturalism, scientific realism, empiricism, and repeatability (see also [3.28, 3.30]).
The suggested extension of the continuity thesis just extends the very same reasoning to noogenesis and subsequent cultural evolution (or gene-culture coevolution; see, e.g., [3.59]). There is nothing spectacularly different here—again, one might reason that noogenesis was a “lucky accident” or a rather regular occurrence whenever all physical, chemical, and biological preconditions exist. It does not matter for the continuity thesis itself and its role as a heuristic that we do not know and do not understand all these preconditions at present. As we gain better insight into those, we will update our understanding and our credence in hypotheses derived from the continuity thesis. It is quite similar to Copernicanism—it was in the beginning a purely philosophical assumption, which gradually obtained support as we gained knowledge about the stellar, galactic, and, in recent years, planetary populations of our universe. Our improved astronomical insights have corroborated the Copernican thesis (with full understanding that it can never be strictly proved). Needless to say, the extended continuity thesis has been implicitly accepted in most SETI studies to date, since any expectation of detecting a radio signal or any other technosignature is based upon the assumption that noogenesis both occurs in naturalistic manner and with a reasonable, non-infinitesimal probability. (In fact, the traditional SETI uses even stronger assumptions, dealing with convergence in cultural evolution; cf. [3.45, 3.65].)
Why is, then, the continuity thesis so often controversial and rejected (the best astrobiological example is, of course, [3.66]), both in the origin of life studies, but also way beyond? Some of the sources of resistance to the continuity thesis and its extensions are rather obvious: creationism, anthropocentrism, and other narcissistic expressions of “specialness” humans are prone to ascribe to themselves. There is a significant literature on the subject, as well as the dire consequences such attitude has in areas such as environmental protection or animal rights (e.g., [3.35, 3.51]). In the rapidly advancing AI (artificial intelligence) field, we may safely assume that at least a part of the downplaying the risk of misused or malevolent AI is exactly due to the same anthropocentric attitude [3.11].
However, there are other sources of recalcitrance and resistance to the continuity thesis which are somewhat subtler and at least as pervasive. One of them is “chronocentrism” or a belief—explicit or implicit—that one’s own epoch is of particular importance among all possible, real, or imaginable epochs. Chronocentrism is formulated and criticized, e.g., by Fowles [3.26] as the belief “that one’s own times are