This is one of my four pages (scientific, thermodynamic,
methodological,
and philosophical) about the
origin of life.
Theories about the origin of life on earth are usually
evaluated in a context of methodological naturalism by
assuming that "everything (throughout the entire history of nature)
happened by natural process." Is
this assumption true, and is
it always useful in
our search for truth?
1. The
Science of Chemical Evolution (Part 1)
An Origin
of Life by Chemical Evolution?
In an attempt to explain
the origin of life, scientists propose a two-stage process of natural chemical
evolution:
1) formation of organic molecules,
which combine to make larger biomolecules;
2) self-organization of these
molecules into a living organism.
For each stage, scientists
are learning that what is required for
life seems much greater than what is possible by
natural process. The huge difference has motivated scientists
to creatively construct new theories for reducing requirements and enhancing
possibilities, but none of these ideas has progressed from speculation
to plausibility.
Later, we'll return to scientific
evidence-and-evaluation in The Science of Chemical
Evolution: Part 2 and Part 3. Before
then, let's look at how scientific evaluation is affected by philosophy.
2. A
Test-Case for Naturalism
Confusion
is caused by the common use of "naturalism" with two meanings: in
a narrow meaning, naturalism is a specific
claim — which is compatible with Christianity — of "only
natural process" for a particular event, series of events, or
period of history; in a broad meaning, NATURALISM (or naturism)
is a general claim — not compatible with Christianity — that "only
nature exists" with matter/energy but with no God and thus no
divine action.
In this page, "naturalism"
has the
narrow meaning. But a wider range of people, including both
theists and non-theists, affirm this narrow meaning. But
non-theists, who hope the general meaning is also true, provide
much of the emotional intensity
and sociological
pressure (in the scientific and educational communities)
for opposing non-naturalistic theories.
For judging
the depth of commitment to naturalism — an
assumption that everything in the history of nature happened by natural
process — the
origin of life makes a fascinating test-case. To
see why, let's compare three characteristics of chemical evolution
and biological evolution.
• Scientific Support? Current
theories about chemical evolution seem highly implausible, so the scientific
support is very weak. But support is much stronger (*)
for biological evolution, for a neo-Darwinian development of biocomplexity
and biodiversity. * the
scientific support is stronger, but is usually overestimated due to a shifting
of support
• Unifying Function? Most
scientists and educators think biological evolution — but not chemical
evolution — plays an important unifying role in biology.
• Worldview Function? Both
types of evolution are necessary for a worldview of naturalism, for a universe
with a natural total evolution (astronomical,
chemical, and biological), with only normal-appearing natural process throughout
the entire history of nature.
Worldview Asymmetry: If
a natural origin of life (of any type, anywhere in the universe) is impossible,
this would be devastating for the worldview of an atheist, deist, or rigid
agnostic. But either way — with or without a natural origin
of life — is fine
for Christians, including me, as explained in my FAQ
for Creation, Evolution, and Intelligent Design (conclusion of 5B,
plus 5C) and No
Proof for the Existence and Activities of
God? Why isn't God more obvious?
When we look at the origin
of life, interesting questions arise from an interesting combination,
because chemical evolution
• is not supported by a logical evaluation
of evidence,
• and is not important for unifying biological
science,
• but is essential for a "no miracles"
naturalism.
This is an opportunity for scientific
humility about naturalism. Is the response a humble acknowledgment
that maybe life did not begin by natural process, so maybe naturalism
is wrong? No, instead there are confident statements (by individuals
and organizations, in textbooks and websites) claiming that chemical evolution
definitely did produce
life, even though we don't yet know the details of how this happened.
This transition between
Sections 2 and 3 is a story about scientists — who are speaking "in
the name of science" for a prestigious organization — making
a claim that is confident but is not scientifically justifiable:
Although a natural origin of life by chemical evolution
seems implausible, the National Academy of Sciences confidently asserts (in Science
and Creationism, 1999) that "For those who are
studying the origin of life, the question is no longer whether life could have
originated by chemical processes involving nonbiological components. The
question instead has become which of many pathways might have been followed to
produce the first cells." This confidence in the power of natural
process doesn't seem consistent with the scientific evidence, so why does the
NAS make the claim? Maybe they are influenced by an assumption, which is
not based on science, that everything in the history of nature happened due to
natural causes.
comments about Sections 3-8:
Originally, this page was a "sampler" that combined a variety of ideas
about science and philosophy. Then I split it into several pages that are
more specialized, that focus on each major idea. In the current page, some
sections (6 & 7) are unchanged, some (4 & 8) are omitted, and others
(3 & 5) include selected excerpts. { Or you can see the entire original
page. }
3. Closed
Science and Open Science
This
section was moved into Methodological
Naturalism but the main ideas (in quoted excerpts, with some minor
revisions) are below:
Methodological Naturalism
and Closed Science
Currently, most scientific inquiry
is closed by methodological naturalism (MN),
a proposal to restrict the freedom of scientists by requiring that they include
only natural causes in their scientific theories. In a closed
science (restricted by MN), evidence and logic are not the determining
factors because the inevitable conclusion — no matter what is being
studied, or what is the evidence — must be that "it happened by
natural process."
Can we avoid the possibility
of unavoidable error?
Imagine two possible worlds: one
has a history of nature with all events caused by natural process, while the
other has a history that includes both natural and non-natural events. In
one of the two possible worlds, a closed science (restricted by MN) must inevitably
reach
some wrong conclusions. (*) By
contrast, in either world a non-MN science will allow, although it cannot guarantee,
reaching
correct
conclusions.
* Logically, MN should
be accompanied by MN-Humility that
acknowledges the possibility of unavoidable error: If
the origin of a feature actually involved a non-natural cause, then any explanation
by MN-Science (in
terms of only natural causes) will be incomplete or incorrect.
The Freedom of Open Science
Imagine that we're beginning
our search for truth with a logically justifiable attitude of humility, by
refusing to decide that we already know — with certainty, beyond any
doubt — what kind of world we live in. If we don't know whether
history has been all-natural, our best scientific strategy for finding truth
is an open science, with scientists humbly asking
a question instead of arrogantly assuming an answer.
In open science... a scientist begins with
an MN-assumption, but does not insist that — no
matter what the evidence indicates — it is necessary to end with
an MN-conclusion. An open scientist adopts testable-MN instead
of rigid-MN, because the assumption of MN is treated
as an assumption, as a theory to be tested rather than a conclusion to be accepted. There
is flexible open-minded inquiry, with freedom of thought for the individual and
community, and scientists are free to follow the evidence-and-logic wherever
it leads. ...
Should science be logical?
Should we let methodological naturalism
force us to accept a "scientific" conclusion that is less logical
... simply because it is natural?
Is evidence irrelevant? MN-Science
can
bypass
the process & claim the support.
The Conclusion
of MN-Science — that no matter what is being studied, or what
is the evidence, it happened by natural process — is
actually The Assumption of MN. The circular logic of MN, which
converts a naturalistic assumption into a naturalistic conclusion, is illogical
(because circular logic is bad logic) yet is unavoidable, and it requires
no science.
To see the irrelevance of evidence
when MN determines the conclusion, compare the evidence-based
implausibility (earned by current theories for a "chemical evolution" origin
of life) with the naturalism-based confidence of
the NAS in claiming that "the question is no longer
whether life could have originated by chemical processes. ... the question
instead has become which of many pathways might have been followed to produce
the first cells." Yes, with MN the evidence is irrelevant. Even
though each of the "many pathways" is
implausible, one pathway must have produced life (because according
to MN this is the only possibility) so confidence does not require evidence. { Words
are carefully chosen by NAS to avoid technical falsity, since they say "could
have originated" and "might
have been followed." But the words are also chosen to clearly
express the claim that "the question is no longer" whether
it did occur naturally, the only question is how it occurred
naturally. }
Of course, the irrelevance of
evidence does not mean there is no evidence, or that MN is leading to the
wrong conclusion. But it does illustrate a logical weakness of MN,
since MN requires that we must reach a scientific conclusion before doing
any science. But instead of acknowledging this logical weakness, usually
MN-Humility is ignored and there is an implication that the assumption made
by MN (that it happened by natural process) is
a conclusion reached by science (and is therefore probably
true). MN provides a way to bypass the process of science and
then claim the authority of science as support.
For example, there is an implication
that the declaration by NAS (speaking with
authority "in the name of science") is based on scientific
evidence and logic. But the main reason for believing that life had
a natural origin is not science, it's a naturalistic assumption
that everything had a natural origin.
Is a closed science theologically
acceptable?
For a Christian who believes that
God can do miracles, as claimed in the Bible, is a closed science (with MN
forcing scientists to assume that no miracles have occurred in the entire history
of nature) theologically acceptable? { "yes" is my answer,
as explained in Methodological Naturalism }
4. What
is a theory of design?
This
is now in Four Types of
Design which describes design (in general,
broadly defined so it includes all four types) and Design (specific,
with a narrow definition that includes only two types).
5. Can
a theory of design be scientific?
Most
of this section is now in Intelligent
Design: Is it scientific? and Methodological
Naturalism and some (re: design and religion) is in Four
Types of Design.
• Design is Testable in Science
Design can be tested using scientific logic. How? When
we use the definitions above, design [narrowly defined] and non-design are mutually
exclusive (it was one or the other) so we can use eliminative logic: if non-design
is highly improbable, then design is highly probable. Thus, evidence against
non-design (against production of a feature by undirected natural process) is
evidence for design. And vice versa. The evaluative status of non-design
(and thus design) can be decreased or increased by observable empirical evidence,
so a theory of design is empirically responsive and
is testable. Based on a logical evaluation
of evidence, we can conclude that a design theory is probably
true (if all non-design theories seem highly implausible) or is
probably false (if any non-design theory seems highly plausible). { But
can design be proved? What about future developments in science? }
• Observable Signs
of Design
• Can historical
science be scientific?
• Design is
Common in Science
• What difference
will it make?
• Will it be
scientifically productive?
• Does it violate
The Rules of Science?
• When is
critical thinking unscientific?
• Why is
it controversial?
• Should you examine
it more carefully?
The arguments for Closed
Science seem less logical when we look more closely ... so the closer we
examine Open Science the better it looks.
The main part of this page ends by looking at current science & future
science, in Sections 6 & 7.
6.
The Science of Chemical Evolution (Part 2)
In an attempt
to explain the origin of carbon-based life on earth, conventional naturalistic
theories of chemical evolution propose
two stages in the transformation of lifeless chemicals into life: 1)
the formation of small organic molecules, which then combine to form
larger biomolecules; 2) the self-organization of these molecules
into a primitive living organism.
Despite initial optimism following
the famous Miller-Urey experiments in 1953, closer investigations have revealed
major problems that have not been solved (and perhaps cannot be solved) in
both stages of the proposed scenario:
In the first stage, chemical equilibria
are usually unfavorable (they are "energetically uphill") for the
formation of small biomolecules and also for their synthesis into larger
biomolecules. During experiments in which there is a realistic simulation
of the atmosphere on an early earth — using the probable starting molecules
(H2O, plus N2 and CO2 which are stable and unreactive) instead of the improbable
starting materials (H2O, plus reactive NH3 and "explosive" H2 and
CH4) in the reducing atmosphere used for the Miller-Urey experiments — the
yields of essential biomolecules are extremely low.
Even if biomolecules could form
in Stage 1, these lifeless chemicals would have reached only the starting
point for the most challenging part of their journey toward life in Stage
2. The simplest "living system" we can imagine, involving
hundreds of components interacting in an organized way to achieve energy
production and self-replication, would be extremely difficult to assemble
by undirected natural process. And all of this self-organization would
have to occur before Darwinian natural selection (which depends on self-replication)
was available.
Basically, what scientists
are learning is that the complexity required for
life (in terms of biomolecule formation and self-organization) seems
to be much greater than the complexity available by
natural process (beginning with lifeless matter). This huge
difference has motivated scientists to stretch their imaginations, to
creatively construct new theories for reducing requirements and enhancing
possibilities.
For example, in an effort to avoid
a "chicken and egg" problem — in modern cells, DNA is required
for protein synthesis, but protein is required for DNA synthesis — scientists
have proposed that RNA (which combines the replicating ability of DNA and
the catalytic activity of proteins) was the key life-producing molecule in
the earliest cells. But this "RNA World" theory now seems
implausible due to the apparent impossibility of pre-biological RNA synthesis,
and because the catalytic activities of RNA have not matched initial optimistic
hopes. In response, scientists are now proposing "pre-RNA World" theories
with key functional roles played by other molecules, and with metabolic energy
sources that would be easier to use.
Other alternatives include variations
on the classic "soup" scenario, with new environments such as a
semi-evaporated pond, a seafloor hydrothermal vent, the surface of a clay-like
mineral, or even another planet. Or the first life in the universe
might have been different than familiar carbon-based life on earth.
Scientists are trying to develop
principles for a prebiological selection of molecules, analogous to the biological
selection of genes in living organisms. And they are continuing to
explore the self-organizing properties of complex chemical
systems, and to search for ways of reducing the minimal complexity
required for a living system.
What is the status of these alternative
theories? So far, none has progressed from speculation to plausibility. But
they do stimulate experimental and theoretical research, and offer the hope
that eventually scientists may discover new principles to serve as the basis
for new theories, and may develop a plausible explanation. But the
major reasons to question chemical evolution come from what we do know about
chemistry and life, not from our lack of knowledge.
There is also a more
detailed version of this section.
Irreducible
Complexity and Minimal Complexity
In Darwin's Black Box:
The Biochemical Challenge to Evolution (1996), Michael Behe illustrates
the principle of irreducible complexity with
a mousetrap that has five interacting parts: a base, hammer, spring,
catch, and holding bar. Each part is necessary, and there is no
function unless all parts are present. A trap with only four parts
has no practical function. It doesn't just catch mice poorly, it
doesn't catch them at all.
What are the evolutionary implications? Behe
says, "An irreducibly complex system cannot be
produced directly... by slight, successive modifications of a precursor system,
because any precursor to an irreducibly complex system that is missing a
part is by definition nonfunctional. An irreducibly complex biological
system, if there is such a thing, would be a powerful challenge to Darwinian
evolution." (Darwin's Black Box, page 39)
For a nonliving system, the
implications are even more challenging, because natural
selection — which is the main mechanism of Darwinian evolution — cannot
exist until a system can reproduce. For the origin of life, we can
think about the minimal complexity that
would be required for reproduction and other basic life-functions. Most
scientists think this would require hundreds of biomolecular parts, not
just the five parts in a simple mousetrap.
7. Can
design be proved?
Although "design
and non-design are mutually exclusive" a design theory
does not claim that non-design is impossible and design is certain,
it only claims that design seems more probable, based on scientific
evidence and logic. This type of probability-based conclusion
is consistent with the logic of science in which proof is
always impossible, even though scientists can develop a logically
justified confidence in the truth or falsity of a theory. In
science, a high level of confidence (not proof) is the goal when scientists
evaluate a theory to determine whether it is worthy of acceptance.
If a design theory claims only
to be "more probable" or to warrant "a high level of confidence" this
is the standard by which it should be judged. It seems unreasonable
for critics of design to demand — along with radical postmodern critics
who challenge the credibility of all science — that if scientists
cannot claim the certainty of proof, they should claim nothing. {a
continuum of theory status}
Is
it rational to consider all possibilities?
All current theories for
a natural origin of carbon-based life seem highly implausible. Is
it rational for scientists to consider the possibility that life on
earth did not originate by undirected natural process, but was the
result of design-directed action? The certainty of "proof" is
impossible because we can never propose and test all possibilities
for non-design. But we could develop a logically justified confidence
that our search has been thorough yet futile, and no promising approaches
remain unexplored.
Logic requires that, during
any intellectually rigorous attempt to explain the origin of an observed
feature, scientists should consider all possibilities. Perhaps
a feature, such as the first carbon-based life in the universe, was produced
by undirected natural process that: 1w)
did occur even though it was extremely improbable (and
therefore it should be rejected as a scientifically plausible explanation, *); or
maybe the natural process was reasonably probable (so
we could reasonably expect it to occur in the available times-and-places *) and
it can be described in a satisfactory way by a naturalistic theory that 1x) is
currently known (whether or not this theory currently seems adequate)
or 1y) could be known in the future,
or 1z) could never be known because
the natural process was too complex or cognitively unfamiliar for humans
to propose. Or maybe the feature was produced by design-directed
action, by 2A) natural design and construction, or 2B)
supernatural design and creation.
* In any scientific
evaluation the "probabilistic recources" must be considered. For
example, in one five-card deal the odds of getting a royal flush are low, 1 in
649,740. If 9 hands are dealt, the odds of getting a royal flush (in any
of the hands) is still low, about 1 in 72,000. But the probabilities are
very different if there are 9 million deals, with the odds becoming a million-to-one
in favor of getting at least one royal flush.
1w* One
speculative theory, which is designed to neutralize all types of DESIGN-claims
(for either a design of nature or design-action during history), proposes that
if an immense number of universes exist, then even the extremely improbable — such
as a universe with properties of nature that naturally allow life and also
produce life — will become highly probable.
Due to possibilities
for a future theory (1y) or no theory (1w, 1w*, or 1z), the implausibility
of current non-design theories doesn't prove the truth of design. And
if scientists want to deny design (as a possibility to seriously consider)
they can do it forever, no matter how advanced their science becomes. For
example, imagine a scientific community with trillions of super-intelligent
space aliens (IQ = 20,000) each having a life span of a billion years,
devoted to science (and using high-speed travel to explore a variety
of environments throughout the universe) for the past 5 billion years,
who have not yet constructed a plausible theory for a natural origin
of life. Even in this situation a denial of design would be possible,
but would it be rational?
In the near future, however,
the actual state of human knowledge will remain much less advanced
than in this imaginary super-science. And critics of design will
point out, with some justification, the reasons for cautious humility
when making claims for design. Regarding the implausibility of
current theories, defenders of non-design say, "please be patient
and eventually our improved scientific knowledge will make non-design
seem more plausible." But is this assumption necessarily
true? Compared with fifty two years ago (when the Miller-Urey
experiments were "hot news" that inspired optimism about
naturalistic theories) now we know more about "origin of life" science,
and what we've learned has made a natural origin of life seem less
plausible, not more plausible.
What
might happen in the future of science?
Even though advocates of
non-design imply that future science will support their claims, the
change in support could go either way, up or down. Will non-design
seem more plausible because we have discovered how a feature could
have been produced by undirected natural process? Or will it
seem less plausible because we have learned more about the limits of
natural process? Either of these results could occur.
In fact, both changes
have occurred in the history of research about chemical evolution. Compared
with 1952, in 1953 our plausibility estimates for a natural origin
of life were higher because the Miller-Urey experiments had converted
inorganic chemicals into small biomolecules. Many scientists
optimistically assumed that we would soon discover a natural production
of large biomolecules that would transform themselves into a simple
reproducing cell which could then evolve and increase in complexity. Since
then, however, the warm glow of optimism has been cooled by the harsh
reality of improved scientific knowledge. The distance between
what is naturally possible (before life) and what is necessary (for
life) seems much greater now than in 1953. An increase in knowledge
has made a natural origin of life seem less plausible, and this has
strengthened the scientific support for a theory of design. In
the future, if our knowledge continues to improve, and if a natural
origin of life continues to seem highly implausible, a claim for
design will become even more strongly supported.
In the future, what will happen
in science, and how will this affect the status of non-design and design? When
thinking about this, we can use our imaginations to predict improvements
in current theories and inventions of new theories. And
we can use current knowledge to guide our questions. Most of the skepticism
about current theories of chemical evolution is based on what we know, and
this knowledge can help us ask specific questions. We can look at each
obstacle to a natural origin of life — such as the unfavorable equilibria
for the chemical reactions needed to make biomolecules, the high degree of
biocomplexity needed for metabolism and reproduction,... — and try to
imagine ways in which future knowledge might change our views about each obstacle. We
can ask, "How likely is each change?" and "How would it affect
our evaluations for a natural origin of life?"
To make good predictions about
future scientific developments, we need creativity (to imagine what could be)
plus criticality (to make realistic predictions about what is probable in reality,
not just possible in our imaginations) so we can avoid the extremes of insisting
that in this area of science "nothing new will happen" or "anything
could happen."
Should
we ask the question?
Design cannot be proved,
but in science the goal is logically justified confidence, not certainty. In
the near future, scientists will disagree about the plausibility of
design. But this is not a cause for concern, because disagreement
is healthy for science when it stimulates productive thinking and research
by advocates for different points of view. And the points of
view should include design. When we ask, "Was design-action
involved in producing this feature?", it will be impossible to
answer with certainty. But it should be easy to decide, "Should
we ask the question?" A curious, open-minded community will
say "YES, we want our science to be flexible and open to inquiry."
8. Questions
and Freedom
• 8A.
Scientific Questions (but not Proof)
This has been moved (in condensed
form but with some new ideas added) into Intelligent
Design: Can it be scientific?
Scientific Evaluation of
a theory: . . .
Philosophical Evaluation of a
theory: . . .
• 8B.
Scientific Freedom (instead of Necessity)
This
has been moved (in expanded form) into Methodological
Naturalism: Is it theologically acceptable?