ENACTMENT: Doubt the feasibility of the fundamental values being what they are. Now realize that your doubting forces them to be that way.
The ACP is an extension of the Goldilocks Principle, which notes that the distance from Earth to Sun is just right for life to occur and evolve into humans. Additionally, the distance from Sun to galactic center, which determines the metallicity of the Sun and the frequency of neighboring supernovae, is also important. Thus any planet that meets these conditions is called a Goldilocks Planet.
The ACP notes that the Earth–Sun distance depends on the whole universe being “just right.” For example, the values and ratios of the four fundamental forces and other observables must be within a particular and narrow range in order for universes to evolve into ones that produce energy sources (stars), planets (greenhouses), and energy sinks (empty space) at the right distances. Why does our universe happen to have the fundamental values it does? How did we get so lucky?
Weak anthropic principle
If our universe weren’t hospitable to life, then we wouldn’t be here to speculate about it. Many universes are born with varying fundamental values. We see this one because it has the right values.
Here, the explanandum is our universe having the fundamental values it does, and the explanans is selection bias operating on an infinite domain of possible universes (the Multiverse). We see only this (type) of universe because it’s the only one that can produce us.
We must be prepared to take account of the fact that our location in the universe is necessarily privileged to the extent of being compatible with our existence as observers.
This version is called weak because it has no creative power, merely selection power. Nearly all universes are not tuned to produce intelligent life, but given enough of them, a small number will have the right values. This one must be one of those.
Barrow & Tipler’s version:
The observed values of all physical and cosmological quantities are not equally probable but they take on values restricted by the requirement that there exist sites where carbon-based life can evolve and by the requirements that the universe be old enough for it to have already done so.
Strong anthropic principle
Since we live in a universe capable of supporting life, only life-supporting universes are possible. The universe is compelled to eventually have conscious and sapient life emerge within it, and the symptom of this compulsion is the fact of our emergence. For a universe-emergent subject to exist, it must be possible to observe some universe—but then the laws and constants of such a universe must accommodate that possibility:
- If I am a cosmosubject (conscious of a universe), then necessarily some universe exists.
- Any universe that generates conscious subjects must have the right fundamental values.
- I am a cosmosubject.
THEREFORE, the universe has the force (and other) values that it does.
The universe (and hence the fundamental parameters on which it depends) must be such as to admit the creation of observers within it at some stage. To paraphrase Descartes, cogito ergo mundus talis est.
Barrow & Tipler’s version:
The Universe must have those properties which allow life to develop within it at some stage in its history.
The force of the must is approached in three ways:
1. “There exists one possible Universe ‘designed’ with the goal of generating and sustaining ‘observers’.”
The universe contains a telos, which is the emergence of this—conscious experience of the universe, ourselves, and our diving into it, learning its laws, and colonizing it with our techne to satisfy biological and cultural teloi of our own, transforming it (locally, at least) into these experiential, aesthetic, evaluating, ethical microcosms of human interest. This, the telos of the universe, is a brute fact that comes with the Big Bang. That is why the fundamental values “must” be what they are.
Paul Davies calls this the Life Principle. It says that universe evolves intelligent life because it contains this as its constitutional telos.
2. “Observers are necessary to bring the Universe into being.”
This is the popular Von Neumann–Wigner Interpretation of the measurement problem in quantum mechanics. This is problem of how it happens that the wave function (or state vector) collapses from its actual but unrealizable nature as a probability distribution of values into one particular realized value. The observables we encounter are all particular. Yet the formalism that drives their becoming, which is real and observed in the double-slit experiment to be a really guiding force, says they are perpetually probabilities. Whence the conversion into particularity?
The observer is what delivers probability over into … the domain of which we are aware. This domain, the physical universe, is dependent on observation to be the way it is—particular in its manifestation. Everything in the universe we observe is an eigenvalue. Thus the universe requires us, in order to come into full-fledged being. There is no point of having a Big Bang of a manifest without including the power of manifestation.
CONCLUSION: If the result is a universe with these fundamental values, then our existence is a necessary condition. (Click here for more speculation.)
3. “An ensemble of other different universes is necessary for the existence of our Universe.”