Essay:Scientific reasoning

Scientific reasoning

There are two kinds of reasoning: deductive reasoning and inductive reasoning. The former relies on causes to derive outcomes; the latter relies on evidence to infer the causes of observed effects. Experimental science is ultimately an inductive process. We observe data (represented by the symbol D), and try to determine whether hypothesis 1 (H₁) or hypothesis 2 (H₂) is a better descriptor of D. The adage science is not a truth search becomes appropriate, since although H₁ may be overwhelmingly favored over H₂, there could be a small probability that H₂ is correct, or that D is flawed.

Unfortunately, we cannot determine with certainty what The Truth is. We cannot make statements such as "We are certain that H₁ is the real deal." We can only say things like "H₁ is vastly more probable than H₂", or, if another hypothesis H₀ is involved, perhaps "H₁ is slightly more probable than H₂, and significantly more probable than H₀."

One important reason that the inductive framework works well is because of its flexibility. We don't adhere to any axioms, so we can reserve the right to change our minds as data accumulates (not easily done with deductive processes!). As more evidence for H₁ accumulates, the more probable it becomes, and the less probable H₂ becomes. Note that H₁ can still far outweigh H₂ even if data inconsistent with both H₁ and H₂ are observed. In that case, we may seek to refine one hypothesis or the other, or perhaps explore another hypothesis H₃. If you're thinking, "Hey, that's just a description of the scientific method!", you are correct. Works pretty good, huh?

The text above could be summed up as science is a search for the best possible model for what we observe, not a search for The Truth. In fact, a reasonable test for whether a discipline is scientific might be that it DOESN'T guarantee truth. If you run into someone who claims to know something for sure, with no equivocation, chances are that the claims are not scientific (even if they are indeed true).

Example

Geocentrism could be "The Truth" instead of heliocentrism, but for that to be the case, incredibly improbable events would have to have occurred. Those improbable events would likely consist of one or both of the following:

• The large amount of data providing overwhelming evidence in favor of heliocentrism over geocentrism is flawed; geocentrism is "truth," but our senses and instruments are somehow "tricking" us into observing data that isn't real.
• A vast conspiracy involving a large number of scientists exists to supress the truth about geocentrism. In this case, the data isn't flawed, it's fabricated.

The person who would adhere to geocentrist theory is thus faced with a quandry: either reject what our senses tell us, or resort to the extra-scientific argument of a massive conspiracy. In other words, geocentrists think that the likelihood of the existence of a vast data-faking conspiracy is greater than the data actually favoring heliocentrism.

Young Earth Creationism

Young earth creationism (YEC), as its proponents admit, relies heavily on deduction.

YECs interpret the first chapter of Genesis as describing a literal six-day creation. They believe that this account is The Truth and accept it axiomatically, just as $2+2=4$ is axiomatic [recall that deduction begins with axioms ("The Truth")]. Their adherence to that particular cosmological model cannot be altered, no matter the quantity or quality of evidence in support of alternatives. As a result, they can't use new evidence to update their relative degrees of belief in the models for the origin of the universe; they are instead forced into the awkward and unenviable position of cramming all the evidence (new or old) into the YEC model.

At present, based on available data, the best current model for the universe is one that involves a beginning around 14 billion years ago or so, and an evolutionary biological process. The evidence for this model (call it M_sci) is overwhelmingly greater than the evidence for the universe coming into being in a six-day interval around 6,000 years ago, which is the basis of the YEC model (call it M_YEC). Whether M_sci in its current form is Absolutely The True Way That Things Came About is beyond the scope of science, and is a question for philosophers and theologians to consider. But notice how the inductive scientific process works: if data are taken that conflict with M_sci, requiring it to be modified, it can easily be accomplished. However, if those data conflict with M_YEC, the YEC adherents have to inject highly, highly improbable scenarios into M_YEC to force the data into the model. Consider the YEC positions about distant starlight and how animals like kangaroos got to Australia after a global flood. Since they're reasoning deductively, they HAVE to perform such logical gymnastics, or their axioms would be violated; it would be equivalent to accepting that $2+2$ no longer equals $4$.

The uniformitarian model and God

YECs frequently argue that the uniformitarian model (what we're calling M_sci) includes an axiom as well; namely, the axiom that God doesn't exist. Really? As shown above, science doesn't rely on such assumptions; it is, at its core, an inductive process. In fact, the existence or non-existence of God is not something that M_sci addresses at all.

It is perfectly plausible that God exists within the framework of M_sci; it's also plausible that he does not. We simply don't have any hard scientific data on the existence of God, and without data we can't update the probability of his existence from a scientific standpoint. Presumably, since God requires faith in his existence, and scientific data strongly indicating his existence would destroy the need for faith, he might not allow such data to be collected anyway.

Furthermore, if data and evidence accumulated for the existence of God, God would be describable by science, and would therefore become a component of M_sci.

The scientific considerations, however, are completely distinct from philosophical or theological considerations, which may (and frequently do) involve God.

See Also

• Deductive reasoning
• Inductive reasoning
• Science
• Religion
• Creationism
• Essay:Bayesian Inference and the Power of Skepticism