Why is an explanation needed?

Fine Tuning of Universe

Sunshine warms our bodies and grows our food. But why do we have sunshine? It occurs because natural processes — which depend on the mass of particles, conversion of mass to energy (e = mcc), rate of nuclear reactions, and sizes of nuclear and gravitational forces — are "just right" to produce a balance between opposing forces. One force pulls the sun's fiery atmosphere inward, while others push it outward, in a cosmic tug-of-war lasting billions of years.
To understand fine tuning, imagine that you are sitting in front of a control panel with dozens of dials. To allow life, each dial — which controls one property of the universe — must be fine-tuned to a specific setting within a very narrow range. You are alive, reading this web-page, because all dials are properly tuned, so we have stable atoms and molecules, stars that produce energy and heavy atoms (our bodies are made from stardust!), the amazing chemistry of DNA, water, and enzymes, and much more.
An amazing discovery of scientists, in recent decades, is that many properties of the universe are "just right" for life. Most scientists are convinced that the fine-tuning constraints on a life-allowing universe are very tight because small changes would make the existence of intelligent life impossible, and that the probability of a universe having these properties (fine tuned to be "just right for life") is extremely low.

TWO THEORIES claim to explain why our universe is what it is:

• Intelligent Design (of one universe)

The simplest causal theory is intelligent design plus design-directed action, with our universe being designed and produced by an extremely intelligent and powerful designer/producer who cleverly designed this universe so it would support life.

• Multiverse (with many universes)

Scientists have analyzed the probability of a universe capable of supporting life-forms that are intelligent, and have estimated the odds to be extremely low. If there is only one universe, and it was not designed for life, we must conclude that we are extremely lucky. But if, as proposed in a Multiverse Theory, we live in a multiverse containing an immense number of universes, and if there enough universes and if their properties are distributed across a wide range, the odds would favor having at least one universe with intelligent life. Basically, a multiverse provides a way to beat the odds.

Intelligent Design is compatible with a Multiverse, a Grand Unified Theory, and the Anthropic Principle:

Does a multiverse require intelligent design?

Robin Collins explains why "even if a ‘many-universes generator’ exists it seems to need to be well designed" in order to produce a multitude of universes with widely varying properties. If this is true, the two most plausible theories are: • one universe that was intelligently designed, or • a multiverse (with many universes) that was intelligently designed. But if you think a multiverse does not need to be designed, an undesigned multiverse is a plausible theory.

Therefore, the choice is not
EITHER design OR multiverse,
but instead is
EITHER designed universe or designed multiverse OR non-designed multiverse,
so currently we have THREE plausible theories, not just two, for explaining the fine-tuned "just right" world we observe:

four combinations	DESIGNED by God	NOT DESIGNED by God
one UNIVERSE (and we live in it)	DESIGNED UNIVERSE is plausible and is an option for theists	UNDESIGNED UNIVERSE is extremely improbable ( practicaly impossible? )
a MULTIVERSE (with many universes)	DESIGNED MULTIVERSE is plausible and is an option for theists	UNDESIGNED MULTIVERSE is plausible and is the only option for atheists

Grand Unified Theory (with Intelligent Design of Nature?)

Some scientists hope that eventually a "grand unified theory of everything" will show why it is necessary for the properties of nature to be what they are. Some atheists are hoping this would support their theory of materialistic non-design. But if scientists do discover/construct a grand unified theory of physics, wouldn't it be more rational to conclude — if there is only one way to combine everything into a set of properties (if the unified theory applies to all universes within the multiverse *) and if this one set produces a universe that allows life — that the universe, operating as described in this elegantly unified theory, has been cleverly designed?
* It would also be rational, as described above, to conclude that a mechanism which produces many universes with widely varying unifying properties, with different unifying properties in each universe, would "need to be well-designed." { To explain the origin of many universes within a multiverse, scientists have proposed many mechanisms, involving string theory, inflationary expansion, general relativity, quantum mechanics (with vacuum energy and bubbles, a "many worlds" interpretation,...), colliding branes, collapsing black holes, and more. }

Philosophical Objections to a Multiverse

Two types of philosophical objections do not provide logical reasons to reject a multiverse theory. One objection — saying "in a multiverse everything would happen and that would be strange," which basically says "I don't like it" — is based on emotion and is not logically impressive. Sometimes the evaluation of a theory by asking "is it simple and elegant?", as in Occam's Razor, can be supported by logic, but not in this case; Occam's Razor should not be used to criticize a multiverse theory that proposes zillions of universes, for the same reason we don't criticize an atomic theory that proposes a million billion billion atoms in a cup of water.

The Anthropic Principle (with or without Intelligent Design of Observers)

Perhaps we should just say "so what?" because if we are observing a universe, it obviously must have properties that allow our existence. This anthropic principle — which states that because humans exist, we must observe a universe consistent with our existence (due to anthropic selection, thus the anthropic selection principle) — is logically valid, and is compatible with either the presence or absence of a designer, so it doesn't favor either of the two theories. {definition of anthropic principle — in four versions}

Can scientific evidence-and-logic help us distinguish between a single universe and a multiverse?

Universe or Multiverse? — Scientific Evidence

According to most multiverse theories, other universes are in a different space-time framework, so in principle they cannot be observed. Or they are very far away, so in practice they are unobservable. Therefore, the fact that we do not observe any other universe does not count as scientific evidence against theories proposing the existence of many other universes. Very convenient.

Divine Design versus Materialism? — Philosophy not Certainty

Why does the universe have properties that allow life? I think the most plausible explanation is that it was designed and created by a divine designer/creator whose intelligence and power are beyond our abilities to comprehend. But this theory cannot be proved (beyond a reasonable doubt) by science or in any other way. Alternative theories, proposing a multiverse, also cannot be proved or disproved by current science, partly because our evaluations are hindered by an absence of empirical data about what existed and what happened before the Big Bang Beginning of our universe. And philosophical objections to a multiverse (such as appealing to Occam's Razor) seem weak and unpersuasive.
Theistic and atheistic worldviews propose different descriptions of reality (and explanations for it), including different ideas about what existed before the beginning of the universe. An atheist assumes the existence of a materialistic capability for creating our universe. A theist assumes the existence of God, who has this capability. Each asks the other, "Can you explain what caused the existence of what you assume as the starting point?" Neither offers an answer that satisfies the other, and neither assumption can be proved, so theism and atheism both offer a possible explanation for what we observe.
If divine design and materialism are both possibilities, and a choice is not forced by logical necessity, the choice can be strongly influenced by personal preference for a particular worldview and its associated philosophy of life.

Divine Design without Proof? — Worldviews and Faith

Should this lack of proof bother us? No. In fact, I think "a state of uncertainty" is the way God wants it to be, because a lack of certainty forces each of us — no matter what we believe in our worldview — to live by faith in what we believe. What is the spiritual significance of this uncertainty, with humans apparently unable to logically prove or disprove the existence and actions of God? Why isn't God more obvious?

If you're curious about questions — Why do scientists think there is a fine-tuning of characteristics, constants, and conditions? Why is an undesigned single universe extremely improbable, requiring a multiverse to "beat the odds"? (and how is this similar to wondering "how can I be almost certain that I'll get a royal flush?") How could a multiverse be produced, and how scientifically plausible is this scenario for cosmology? How could different universes have different properties? Where are the other universes? If an active God does exist, why hasn't he provided proof for his existence and activity? — these questions are examined in more detail (with the help of ideas from Robin Collins, Victor Stenger, and William Lane Craig) in Part 2 of Anthropic Principle, Fine Tuning, and Theology: Multiverse and/or Intelligent Design. Or you can look at pages by a wider variety of authors in the homepage for Intelligent Design of Nature & Origin of The Universe.

APPENDIX

Properties depend on Characteristics, Constants, and Conditions:
CHARACTERISTICS — matter/energy (from quarks or strings?) in elementary particles (protons, electrons,...), + and - charge, wave/particle duality and resulting quantizations, space & time, four forces, causal relationships (summarized by Newton, Einstein,...), ... ;
CONSTANTS — for sizes (of energy quantization, four forces, charge & mass of particles,...);
CONDITIONS — initial rate of expansion after Big Bang, initial excess of matter over antimatter, ...

Beating the Odds
The principle is simple. If enough universes exist, everything that can happen will happen!
For example, in a five-card poker hand the odds of getting a royal flush are 1 in 649,740. But with 450,365 deals, your chance of getting a royal flush is 50%. And as the number of opportunities increase, your odds improve dramatically; with 9 million deals (only 20 times the 50% break-even number) the odds are a million-to-one in your favor!
A multiverse can "explain away" all evidence for intelligent design, at any level: for a fine-tuned universe, a natural origin of life, or you winning 10 straight lotteries. For example, IF the probabilities are 10^-2000 for a life-allowing universe and 10^-1000 for a natural origin of life within such a universe, giving an overall probability of 10^-3000, all we need is 10³⁰⁰² universes (if properties are widely distributed,...) and life becomes a statistical certainty, with odds of 10⁴³-to-one in favor of life. *
If the life is intelligent enough to ask "why are we here" the specific universe where this occurs (due to the anthropic selection principle) would seem "special", and if the life is less intelligent the universe would still be special and rare, even if this is not recognized by the life within it.
* Due to a lack of experience, it's difficult for us to understand the immense size of these numbers; we're unable to visualize 10⁴³, and 10³⁰⁰² is MUCH larger but is not infinite.
an IOU — This section will be revised to include the crucial distinction between "an immense number of universes" and "an infinite number of universes", between immensity and infinity, between claiming that "EVERYTHING... will happen" (as I mistakenly say above, assuming infinity) and "MANY THINGS will happen" (this is a better claim, assuming an immense number of universes but not an infinite number).

Occam's Razor and Theory Simplicity
A multiverse does not violate Occam's Razor, which is a principle used to evaluate theories. Occam's Razor states that in a scientific theory "one should not increase, beyond what is necessary, the number of entities required to explain anything. (source)" Here, "the number of entities" can refer to the number of types of entities (not the absolute number) proposed by a theory, or the logical structure of a theory.
Regarding the difference between types of entities and their absolute number, here is a useful analogy: A multiverse theory should not be criticized for proposing zillions of universes, for the same reason that atomic theory is not criticized for having a large "number of entities" when it proposes that 10²⁵ atoms (more than a million billion billion) are in a cup of water.
Regarding theory structure, Victor Stenger explains: "Some theologians and scientists dismiss the notion [of a multiverse] as a gross violation of Occam's razor. It is not. No new hypothesis is needed to consider multiple universes. In fact, it takes an added hypothesis to rule them out — a super law of nature that says only one universe can exist. But we know of no such law, so we would violate Occam's razor to insist on only one universe." In the future, perhaps science will conclude that either a multiverse is impossible, or a multiverse is necessary. But currently "the jury is still out" on this question.
Occam's Razor doesn't seem relevant for thinking about a multiverse, so in this context it's mainly an aesthetic objection. But it can be useful for evaluating the logical structure of a scientific theory. For example, a theory with 500 parameters (so it can explain 500 experiments) will be disliked by most scientists because it is not "simple and elegant"; instead, it seems to be "an inelegant patchwork of ad hoc components that have no apparent function except to achieve empirical agreement with old data." (quoted from my Model of Scientific Method)

Four Definitions of Anthropic Principle

The term "anthropic principle" was introduced in 1973 by Brandon Carter. Later, distinctions were made between four anthropic principles: Weak and Strong (by Carter), Participatory (John Wheeler), and Final (John Barrow & Frank Tipler, 1986, in The Anthropic Cosmological Principle).
WEAK Anthropic Principle (WAP): We can exist because intelligent life requires a universe with a special set of properties, which (of course) we do observe.   ( This "basic anthropic principle" is logically correct, but it doesn't help us determine if our world is designed, as explained above. )
STRONG Anthropic Principle (SAP): The universe must have the properties that are needed to produce life, i.e. a universe without life is impossible.   ( Does SAP propose an intelligent design of our universe? Does it claim that a multiverse is impossible, since most universes in a multiverse would not have life? Or would the SAP-requirement apply only to the multiverse as a whole, by claiming that a multiverse without life is impossible? )
PARTICIPATORY Anthropic Principle (PAP): The eventual emergence of observers is necessary to bring our universe into existence.   ( This theory is based on a wildly speculative philosophical interpretation of quantum physics in which an "act of observation" produces reality, so "if no observers then no reality." This speculation is not supported by the science of quantum physics. )
FINAL Anthropic Principle (FAP): After intelligent life has emerged in the universe, it will never die out.   ( Barrow & Tipler also claim that life will evolve toward an Omega Point when "the totality of life... is omnipotent, omnipresent, and omniscient" in a pantheistic version of God. Martin Gardner calls this the Completely Ridiculous Anthropic Principle, CRAP, and I agree that life will not evolve into God, and that never-ending life is not naturalistically inevitable, it is guaranteed only if God wants it to happen and makes it happen. )

Homepage for Intelligent Design of the Universe

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THE ANTHROPIC PRINCIPLE,

COSMOLOGY and THEOLOGY,

INTELLIGENT DESIGN and/or A MULTIVERSE ?