In astrophysics and cosmology, the anthropic principle is the philosophical consideration that observations of the physical Universe must be compatible with the conscious life that observes it.

Some proponents of the anthropic principle reason that it explains why the Universe has the age and the fundamental physical constants necessary to accommodate conscious life.

The strong anthropic principle ( SAP ) as explained by Barrow and Tipler ( see variants ) states that this is all the case because the Universe is compelled, in some sense, for conscious life to eventually emerge.

Critics of the SAP argue in favor of a weak anthropic principle ( WAP ) similar to the one defined by Brandon Carter, which states that the universe's ostensible fine tuning is the result of selection bias: i. e., only in a universe capable of eventually supporting life will there be living beings capable of observing any such fine tuning, while a universe less compatible with life will go unbeheld.

The anthropic principle states that this is a necessity, because if life were impossible, no one would know it.

The term anthropic in " anthropic principle " has been argued to be a misnomer.

The anthropic principle has given rise to some confusion and controversy, partly because the phrase has been applied to several distinct ideas.

The anthropic principle is often criticized for lacking falsifiability and therefore critics of the anthropic principle may point out that the anthropic principle is a non-scientific concept, even though the weak anthropic principle, " conditions that are observed in the universe must allow the observer to exist ", is " easy " to support in mathematics and philosophy, i. e. it is a tautology or truism

Steven Weinberg and a number of string theorists ( see string landscape ) have used this as evidence for the anthropic principle, which suggests that the cosmological constant is so small because life ( and thus physicists, to make observations ) cannot exist in a universe with a large cosmological constant, but many people find this an unsatisfying explanation.

Again, the anthropic principle states that we can only live in one of the universes that is compatible with some form of intelligent life.

A somewhat similar belief today is anthropic principle, but it only states that laws of physics are useful.

He also states that "... ' anthropic ' reasoning fails to distinguish between minimally biophilic universes, in which life is permitted, but only marginally possible, and optimally biophilic universes, in which life flourishes because biogenesis occurs frequently ..." Among scientists who find the evidence persuasive, a variety of natural explanations have been proposed, e. g., the anthropic principle along with multiple universes.

Known as the anthropic coincidence or fine-tuned universe, it simply states that the large numbers in LNH are a necessary coincidence for intelligent beings since they parametrize fusion of hydrogen in stars and hence carbon-based life would not arise otherwise.

The Self Indication Assumption ( SIA ), a philosophical principle defined by Nick Bostrom, one of the two major schools of anthropic probability ( the other being the Self-Sampling Assumption ( SSA )), states that:

Anti-mechanists argue that anthropic mechanism is incompatible with our commonsense intuitions: in philosophy of mind they argue that unconscious matter cannot completely explain the phenomenon of consciousness, and in metaphysics they argue that anthropic mechanism implies determinism about human action, which ( they argue ) is incompatible with our understanding of ourselves as creatures with free will.

The weak anthropic principle could then be applied to conclude that we ( as conscious beings ) would only exist in one of those few universes that happened to be finely tuned, permitting the existence of life with developed consciousness.

:: John Archibald Wheeler's participatory anthropic principle says that consciousness plays some role in bringing the universe into existence.

A pair of papers by Katherine Mack that appeared on the arXiv in November 2009 casts doubt on the existence of the QCD axion lighter than μeV scale, arguing that ( 1 ) cosmological observations imply that the existence of such a light axion creates a greater fine-tuning problem than the one that it was hypothesized to solve and ( 2 ) that anthropic arguments do not alleviate this fine-tuning problem.

In situations where the existence of the observer or the study is correlated with the data observation selection effects occur, and anthropic reasoning is required.

The Multiverse hypothesis assumes the existence of many universes with different physical constants, some of which are hospitable to intelligent life ( see multiverse: anthropic principle ).

In this way, top-down cosmology provides an anthropic explanation for why we find ourselves in a universe that allows matter and life, without invoking the existence of the Multiverse.

The anthropic principle is a controversial argument of why the fine-structure constant has the value it does: stable matter, and therefore life and intelligent beings, could not exist if its value were much different.

They believe that quantum wave-functions do not collapse like the Copenhagen interpretation holds, nor that each collapse actually buds off separate universes ( like the quantum multiverse hypothesis holds ) but rather that the universe is a participatory universe: the entire universe exists as a single massive quantum superposition, and that at the end of time ( in the open universe of the Xeelee Sequence, time and space are unbounded, or more precisely, bounded only at the Cauchy boundaries of " Time-like infinity " and " Space-like infinity "), when intelligent life has collected all information ( compare the Final anthropic principle and the Omega Point ), and transformed into an " Ultimate Observer ", who will make the " Final observation ", the observation which collapses all the possible entangled wave-functions generated since the beginning of the universe.

The thesis in anthropic mechanism is not that everything can be completely explained in mechanical terms ( although some anthropic mechanists may also believe that ), but rather that everything about human beings can be completely explained in mechanical terms, as surely as can everything about clockwork or gasoline engines.

Antony Flew, who spent most of his life as an atheist, converted to deism late in life because of the anthropic principle.

* The anthropic fine tuning of the universe: He quotes with approval Freeman Dyson, who said " 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 " and suggests there is a wide consensus amongst physicists that either there are a very large number of other universes in the Multiverse or that " there is just one universe which is the way it is in its anthropic fruitfulness because it is the expression of the purposive design of a Creator, who has endowed it with the finely tuned potentialty for life.

The second option, common amongst philosophers who adopt anthropic mechanism, is to argue that the arguments given for incompatibility are specious: whatever it is we mean by " consciousness " and " free will ," they urge, it is fully compatible with a mechanistic understanding of the human mind and will.

Many ancient polytheistic religions, such as that of Ancient Greece, featured strongly anthropic gods, who experienced human emotions, took on human-like forms, and interacted with humans and with one another in human ways.

However, the anthropic nature of the various deities that were worshiped differed among other peoples like the Egyptians and Babylonians, who sometimes thought that their gods could take an array of forms, some non-human.

Bonny Susan Hicks ( 5 January 1968 – 19 December 1997 ) was a Singapore Eurasian model who gained her greatest notoriety for her contributions to Singaporean post-colonial literature and the anthropic philosophy conveyed in her works.

* 1961 — Robert Dicke argues that carbon-based life can only arise when the gravitational force is small, because this is when burning stars exist ; first use of the weak anthropic principle

This provided a simple scientific interpretation of the cosmological anthropic principle: Our world may consist of different parts, but we can live only in those parts of the multiverse which can support life as we know it.

In order to do it, one would need to prove that only one of the many vacua of string theory is actually possible, and to propose an alternative solution of the many problems which can be solved by using the anthropic cosmological principle in the context of the theory of inflationary multiverse.

The hypothetical concept of the anthropic landscape in string theory follows from a large number of possibilities in which the integers that characterize the fluxes can be chosen without violating rules of string theory.

You can only be born into one, so the indifference principle within this ( humans-across-universes ) reference class would mean that the chance of being born into a particular universe is proportional to its weight in humans, N. ( Echoing the weak anthropic principle.

Since an anthropic being is inherently one that can be related to personally, anthropotheism can be seen as the simplest form of " personal god ".

This has prompted attempts at anthropic explanations of the values of some of the dimensionless fundamental physical constants.

This approach has led to considerable research into the anthropic principle and has been of particular interest to particle physicists, because theories of everything do apparently generate large numbers of universes in which the physical constants vary widely.

A speculative solution is that many or all of these possibilities are realised in one or another of a huge number of universes, but that only a small number of them are habitable, and hence the fundamental constants of the universe are ultimately the result of the anthropic principle rather than a consequence of the theory of everything.

* 1968 — Brandon Carter speculates that perhaps the fundamental constants of nature must lie within a restricted range to allow the emergence of life ; first use of the strong anthropic principle

Astronomical existential risks might similarly be underestimated due to selection bias, and an anthropic correction has to be introduced.

Explanations often invoked to resolve fine-tuning problems include natural mechanisms by which the values of the parameters may be constrained to their observed values, and the anthropic principle.

Though the snake occupies a relatively broad range and is not endangered as a species, it is thought to be in general decline largely due to anthropic disturbances.