The anthropic principle, which rose to popular­ity in the 1980s, is conspicuous among attempts at answering the question of the position of human beings in the universe. The application of the principle basically means determining limiting suppositions of models of the universe that must respect its recent state, deductive without contradictions from the past states. Real existing phenomena in the universe, espe­cially the existence of an observer, a human being (which gave the name to the principle), act as strongly limiting suppositions of the selection of all possible states of the universe in its past. This entry reviews the sources of those considerations.

Starting Points

The starting points could be divided in at least two related groups: the existential and epistemo­logical causes of the anthropization of the uni­verse. The existential sources could be briefly characterized by the word surprise: surprise of human beings at the “starry sky above,” astonish­ment provoked by the organization of the sur­rounding world, as if waiting for guests at a prepared table. The surprise does not diminish with the increasing knowledge of nature and its laws; rather, the surprise is increased by the fact that humans do not deal with a single improbabil­ity but with a chain of improbable events during the whole history of the universe, starting with the big bang until the present. For example, the ele­ments and anti-elements’ ratio during the moments close to the beginning of the expansion of the uni­verse had to allow, after reciprocal annihilation and radiation, precisely the quantity of elements remaining as the building material for the uni­verse. This universe can be neither too dense (it would collapse again to the singularity) nor too thin (the matter would then spread out quickly and there would be no material for construction). At the same time, the presently observed stars had to be preceded by the stars of the first generation that created heavier chemical elements and dis­persed them after their annihilation to the sur­rounding space where these elements could become building stones of emerging planetary systems. The created planets must be at an optimal dis­tance from the central star, which must have a relatively stable form. Tolerated deviations—the range enabling the creation of life and basic phys­ical interactions—are expressed by fractional parts of a percentage, while the physical possibility of these deviations is expressed in tenths of a per­cent. The real macrospace must have exactly three dimensions; no other physically possible case allows the existence of life. There is also the numerical coincidence: the size of proton 10²⁷ centimeters and the size of the observed universe 10^-27 centimeters.

As it concerns the accuracy of the “setting” of the speed of the expansion of the universe (for example), even a deviation that ranges from 1:10³⁰ to 1:10²⁹ would mean the existence of the universe without life. Is it all just a coincidence, very improbable, yet still a coincidence? Or is it an impact of something that is beyond reach, some­thing humans are not able to embrace with knowl­edge, which, despite all progress, is still limited?

Versions

1. Carter, who named the principle, formulated its two basic versions in 1968:

Weak—The presence of observers in the universe determinates its time dimension; the universe has to be at least as old as to allow the emergence of an observer. The existence of the observer is thus the determinant for statements concerning the physical state of the universe and the conditions that enable this proper existence. The concatenation of this type of condition offers the most probable picture of the past of the universe.

Strong—The presence of an observer determines not only the time dimension of the universe, but also the whole system of features. The strong version states that in every physically real universe, an observer must once appear, so every universe has to create the conditions for the existence of observers.

In the following years, the proponents of the anthropic principle modify the formulations and two completely new versions appear:

Participatory—This version puts the universe and the observer on the same level; their existence is thus conditioned reciprocally. The version stems from the fact that physically possible states of the universe allow life in only a very narrow range, and the prob­ability of the realization of the universe in this nar­row zone is very limited (a slight deviation and the universe would still exist, only without any life); even lower probability could be found in the pre­sumption that these particular improbable relations would organize in a chain of continuous conditions that would culminate with the creation of an observer. Based on the final improbability, the par­ticipatory version of the anthropic principle draws the conclusion that reason had to participate in the realization of the present improbable state of the universe. There is, however, no explicit mention of the Reason-Creator. Rather an analogy can be observed with the knowledge of micro and macro worlds; for example, in the physics of elements, in the same way as the subject becomes an inseparable part of the object during the observation and makes a natural part of the macro world, it is possible to find the subject in the mega world when its past and recent structures are studied. Nevertheless, if the statement is hidden or explicit in the strong and weak version of the anthropic principle, a double understanding of the role of the subject in the uni­verse can be observed.

1. Ontogenetic role. In the literal meaning, the spirit is considered as the crucial agent in the construc­tion of the universe. “The more I examine the universe and the details of its architecture, the more evidence I find that the universe in some sense must have known we were coming” (Freeman Dyson, The Argument from Design: Disturbing the Universe, 1979). Why is the spirit “favorable” to life and intelligent observers, and why does it construct a universe where the observer is wel­come? (The response is right at hand: The spirit creates according to “its own image.”)
2. Noogenetic role. The spirit realizes the universe by accumulating its knowledge. This interpretation refers directly to the example of the position and role of the observer in quantum mechanics: “A phenomenon is not a phenomenon without being an observed phenomenon. Observers are necessary to bring the universe into existence” (John Wheeler in the discussion on the congress of cosmology, Krakow 1973. ptta.pl/pef/angielski/hasla/a/pdf). The universe is real only when it includes its observer; if it is real, the uni­verse must be able to welcome this observer.

According to the participatory version, the exis­tence of the universe is as important for the observer as is the existence of the observer for the universe. If the universe is supposed to be real, it must have qualities that would enable the exis­tence of the observer.

Intelligent observer—The fourth and the last version of the anthropic principle is its final version: Intelligent systems of processing information have to appear in the universe, and they will never disappear after their emergence. An intelligent observer is the aim because it gives meaning to the existence of the universe.

As previously mentioned, in the background of all these interpretations of the anthropic principle is the surprise at the character of the universe that allows the creation of life, while it would be more probable to dispose of at least slightly different features. Why did the universe “choose,” out of many possibilities available at every moment of its evolution, such a slightly probable succession that led to the creation of life? If the question is asked in the sense of the weak version of the anthropic principle and if its heuristic value is used, then the question “why” is appropriate because it offers a possibility to choose out of the number of possibilities only those that lead to the creation of life, which undoubtedly exists, in order to complete the picture of the past of the uni­verse that best describes the past events. The question becomes more problematic when the strong or the participatory version of the anthropic principle is considered, because the answer is looked for in the activity of the spirit that is “responsible” for all. However, that means only that the primary “why” falls apart into many other questions that cannot be principally answered. The original surprise that had a positive constructive character as it led to the research of the most probable version of the image of the universe is gradually, in its consequences, chang­ing into uncritical astonishment and resignation to continue the research.

While the main point from which the strong, and especially the participatory, version of the anthropic principle start is the improbability of the state of the universe, there is another solution available. The French astrophysicist M. Lachieze-Rey problema- tizes the proper notion of probability: “As it con­cerns the original and continuous setting of the condition of the universe, we do not have (apart from the law of the increasing entropy) any precise law of probability and we can hardly decide what data are probable. We do not know what we would like to know.” (M. Lachieze-Rey, C.N.R.S. Institute d’astrophysique, private communication, Paris 1991) Another possible answer is offered by the inflation theory of the universe. The inflation theories are used as a more physical solution and they are put in opposition to the anthropic principle; however, based on preceding experience, it would be more prudent and appropriate to avoid the excluding “either-or” (for what remains, I will try to show that such an extreme solution has not been fruitful) in order to try to unite the positive features of both perspectives. What solution will offer this proposi­tion? Especially, the earlier-mentioned surprise at the readiness of the universe for life will obtain again its constructiveness, and it will be possible to use the heuristic characteristics of the weak version of the anthropic principle. The fact that the inflation theory studies the possibility of the existence of an infinite number of physically independent universes with variable physical parameters changes the improba­bility into a highly probable phenomenon, if not a statistical need. Most of these independent universes have physical conditions that do not allow the cre­ation of life, but it is not surprising that there has been at least one universe in the infinite number that unites a combination of conditions that enable life. Human beings should not be surprised at having appeared just in this “vital” universe. It remains “just” to disclose the past of the real universe with respect to the fact that past states had to contain such qualities that led to the creation of life; they had to be “biogenetic.” Among these physical solutions are not entirely proved but promising theories, for example, Linde’s modification of inflation models.

This work on inflationary models showed that the present state of the universe could have arisen from quite a large number of different initial con­figurations. This is important, because it shows that the initial state of the part of the universe that we inhabit did not have to be chosen with great care. (Stephen Hawking, A Brief History of Time: From the Big Bang to Black Hole)

Moreover, according to Stephen Hawking, “Must we turn to the anthropic principle for an explanation? Was it all just a lucky chance? That would seem a counsel of despair, a negation of all our hopes of understanding the underlying order of the universe.” (Stephen Hawking, A Brief History of Time: From the Big Bang to Black Hole)

Even if the anthropic principle is not motivated by anthropocentrism, a common ground can be found. The whole history of cosmology—from ancient his­tory until the present—is basically, in a rough scheme, a history of the dethroning of humans from the center to the periphery of the universe. The anthropic prin­ciple seems to restore the privileged position of human beings, their reason and life, by saying that the history of the universe led to the creation of human beings. Nevertheless, related to the inflation theory, the anthropic principle offers results that cor­respond to the previous tendency (concerning the spatial forms of centrism), more precisely expressed— results that correspond even more that anyone could ever imagine. It makes insignificant not only human beings but also the whole universe that can appear only as one of many universes. The partisans of the anthropic principle would certainly protest against mentioning the anthropic principle in the context of anthropocentrism. It is true that the anthropic prin­ciple does not place human beings in the center, but living observers, whatever planet they live on. However, that does not change the fact that the idea of the center is conserved where the subject of knowl­edge is central, whether it is a human being or any other existing thinking being. A comparison can be made between Aristotle and the anthropic principle. The compatibility of Aristotle’s considerations and the anthropic principle could be observed in the applied method that leads to the idea of the privileged position of subject. Thanks to the observation of a falling stone, Aristotle came to the conclusion that heavy objects tend to fall down and that the earth, not able to fall anywhere because of its heaviness, forms the center of the universe; it is the “down” for everything else. The anthropic principle stems from the simple presumption that an observer does exist. To ensure the existence of the observer requires spe­cific, precisely defined conditions. To “offer” these conditions in a certain moment, the universe had to be precisely limited in its past and realize many, even very improbable, possibilities. This fact leads the fol­lowers of stronger versions of the anthropic principle to the conclusion that the universe is oriented to the creation of life, which had to appear. Some of them are even persuaded that the spirit directly participates (ontogenetically or noogenetically) in the construc­tion of the universe appropriate for life.

Aristotle’s stance and the anthropic principle stem from the irrefutable arguments, purely empirical ones (a stone falls down, observer does exist), and lead to the idea of a privileged position of human beings in this universe; in the case of the anthropic principle, which is a far more large-scale framework than Aristotle’s was, the idea is still maintained that a thinking being in particular and life in general hold a privileged position in this cosmos.

Inevitability

Are humans actually able to create a non-anthro- pocentric image of the universe? The proper essence of the cognition process—principal epistemological anthropocentrism—leads to the assumption that every image created by human beings will bear the traces of its producer. If we suppose that the real universe exists and is unique, we have to realize continuously our subjective role in the formation of the image of the world, and we have to get rid of the illusion of objective knowledge that reflects reality and consider as more adequate the one that would consciously include itself and its creator. It is obvious that even in this case, we could obtain approximate results only. In a possible solution of the anthropocentric principle, it would mean acknowledging that the universe is anthropic and non-anthropic at the same time.

Just as a distinction can be made between the final and the limited, thanks to the relativistic physics of spacetime and modern cosmology— even the pair “final and infinite” is only a relative opposition—some other polarities previously con­sidered irrefutable should now be abandoned, including yes or no, white or black, man or woman, word or action, subject or predicate, anthropic or non-anthropic. We humans are continually con­fronted with the dualities of the world; however, we have to realize that they are the dualities of our world, the world of human scale. To what extent is this “yes or no” perspective useful in other, com­pletely different levels? In the world of elementary particles and galaxies? Nevertheless, even “our” world corrects its own oppositions in many ways. What used to be good could be bad today; a friend could behave as an enemy; the disguises of love and hate are hard to recognize. The universe is anthropic in terms of what we know about it and non-anthropic in our ignorance of it.

Josef Krob

See also Aristotle; Cosmogony; Hawking, Stephen;

Teleology

Further Readings

Barrow, J. D., Tipler, F. J., & Wheeler, J. A. (1988). The anthropic cosmological principle. New York: Oxford University Press.

Carter, B. (1990). Large number coincidences and the anthropic principle in cosmology. In J. Leslie (Ed.), Physical cosmology and philosophy (pp. 291-298). New York: Macmillan. (Reprinted from Confrontation of cosmological theory with astronomical data, by M. S. Longair, Ed., 1974, Dordrecht, The Netherlands: Reidel)

Peebles, P. J. E. (1993). Principles of physical cosmology. Princeton, NJ: Princeton University Press.

Polkinghorne, J. (1998). Belief in God in an age of science. New Haven, CT: Yale University Press.