The anthropic principle postulates that our universe is selected for the presence of consciousness in it. I cite Wikipedia:

the anthropic principle is the philosophical argument that observations of the physical universe must be compatible with the conscious life that observes it

To make the anthropic principle precise, it would seem we have to ask what exactly consciousness is. Is this the case? If so what are the criteria used to judge if a configuration of the universe contains consciousness within it?

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  • Related to Can (or How) Anthropic Principle be Made into a Scientific Theory?, only marginally related to physics and (as I said before) a topic on which philosophers, mathematicians, scientists and theologians have been arguing at book length for decades. – dmckee Sep 30 '11 at 17:24
  • In many applications of the anthropic principle, the dividing line is between universes in which any sort of structure at all exists (atoms, galaxies), and those where it doesn't. So only a very weak assumption is made - that "structure" is necessary for the existence of "observers". – Mitchell Porter Oct 1 '11 at 1:58
  • +1, an interesting question; you might clarify which of the several variations of the principle you are interested in here, as they really are quite different in terms of their implications and scope. Just in passing, I might note the community has covered some of this ground already -- cf. What signs indicate consciousness...?. – Joseph Weissman Oct 1 '11 at 2:42

While the term consciousness can have a range of specific and complex meanings in philosophy, I'm afraid in this case simply means awareness. The anthropic principle as stated in the question uses one of the most basic relations in deductive reasoning:

  1. We are observing the physical universe.
  2. In order to observe the physical universe, we must be aware (conscious) of it.
  3. In order to be aware (conscious) of it, it must be compatible with (conducive to) our conscious lives. I.E., the physical universe must be compatible with our consciousness which is observing it.

In other words, by the fact that we are aware of the our physical universe, we can infer that it is compatible with us.


  1. the state of being aware of one's own existence, sensations, thoughts, surroundings, etc.

Source: Dictionary.com


The anthropic principle postulates that our universe is selected for the presence of consciousness in it

This is, of course, a tautological argument.

Let us take the example of some flower which appear white to us, but which actually have stripes and other patterns in infrared colors, visible to bees. To us, at least up until the last century, the flowers are white; to the bees, the flowers are striped; now that we have instruments capable of registering infrared light, the flowers are striped for us as well.

With this in mind, let us ask: what assurance do we have that the universe does not possess all kinds of attributes, patterns, objects, entities, etc., that are not observable by our senses (or the instruments we have invented to extend our sense-perception)? The answer, of course, is none: to use Rumsfeld's schema, we have no way of even beginning to assess the size of the unknown unknowns.

Which means, of course, that what we call "the universe" is nothing more (or less) than "the portion of the universe knowable by us". And this is necessarily always the case.

So, there's no need for a rigorous definition of "consciousness" in this regard; what is relevant is the limits of our sense-perception (as extended by whatever technologies we have developed.)

And, the criteria to judge whether or not a configuration of the universe has consciousness in it is: yes. Since we're talking about it, it does. If it didn't, we wouldn't be capable of raising the question.

  • What would you say of an alternative world in which a certain lineage of bipedal primate was wiped out by an asteroid strike two million years ago? That world would still support consciousness (in the sense that it doesn't differ enough to be incapable of supporting us); it merely wouldn't feature us. It is necessarily not the world we experience, but it is a conceivable one. If you adopt certain ontological positions, it's even one that has been realized; just not one which was realized "for us", relative to our percepts. Is your argument that such counterfactuals are meaningless? – Niel de Beaudrap Oct 1 '11 at 19:08
  • To put it another way: were the flowers striped before we knew what wavelengths to look for the stripes in? If so, we can infer (or at least confidently posit) things that we never percieved. Is a plausible proposal that the universe necessarily evolved in such a way that beings such as ourselves would posit things about it? – Niel de Beaudrap Oct 1 '11 at 19:11
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    I do argue that such counterfactuals are pretty much meaningless; if the sense-perceptions of the other bipedals were similar to ours, we gain nothing; if they are irreducible to ours, they are beyond our comprehension (by definition). As for the latter question: the universe came to pass in such a way as we are here to discuss it. Necessarily? No, of course not. But, tautologically, if it hadn't, we wouldn't be discussing it. As Sidney Morgenbesser famously replied to the question of Why is there something rather than nothing?: "And if there were nothing, you'd still be complaining!" – Michael Dorfman Oct 1 '11 at 19:22

I think you are raising a good point and that it is related to a philosophical problem known as "hard problem of consciousness", indeed it's not clear whether there is anything in the physical laws which implies that a human living brain must experience "consciousness" instead of being just a input-output machine (although with an high degree of complexity).

However I suppose that one could rephrase the antropic principle in a weaker (and less problematic) form where instead of speaking of "consciousness" you speak of brains.

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