Clarification and amplification of a parenthetical assertion
in my essay,
"Why Should We Trust the
May 15, 2017
(Note: This is a first approximation. Additional research
and revision is in order). (5/11/17)
The principle of falsification: To be both meaningful and true, a
statement about empirical reality must not only describe the world as it is,
it must also, by implication, describe conditions in the world that would be
found if the statement were false. As I stated in my essay, "Why Should We
Trust the Scientist," when making a fact claim one must be prepared to say,
"expect to find such-and such empirical conditions, to the exclusion of
other describable conditions."
Today, many esteemed philosophers of science tell us that the
falsifiability criterion is logically flawed. My reply: they are correct,
but it doesn’t really matter. The criterion, though imperfect, remains
robust and essential to scientific inquiry.
This reply requires an extended and somewhat technical justification,
which is why I could not include it in the aforementioned essay.
To begin, formal logical inadequacy is not a barrier to
empirical science. As David Hume demonstrated, induction, the foundation of
such science, is based upon logical fallacies – three in particular: circularity, generalization,
and argument by authority. We will return to this point.
Let’s begin with some elementary logic.
At it’s root, a scientific proof by experiment or observation has the
elementary form of the so-called hypothetical proposition, "if P, then Q."
Affirm or deny the "P" (the "antecedent"), or affirm or deny the "Q" (the
"consequent") and you will on get an "hypothetical syllogism." There are
four possible forms, two of which are valid, and two of which are invalid.
1) If P, then Q. P. Therefore Q. (Affirming the antecedent.
2) If P, then Q. Not P. Therefore, not Q. (Denying the
3) If P, then Q. Not Q. Therefore not P. (Denying the consequent.
4). If P, then Q. Q. Therefore P. (Affirming the consequent.
These rules can be demonstrated by simple interpretations:
1) If John has a son, then John is a parent. In fact, John has a
Therefore John is a parent.
(Valid. Given the premises and conventional
definitions, the conclusion is inescapable)
2) If John has a son, then John is a parent. In fact, John has no
Therefore John is not a parent.
(Invalid: he might have a daughter).
3) If John has a son, then John is a parent. In fact, John is not
Therefore John has no son. (Valid).
4) If John has a son, then John is a parent. In fact, John is a
Therefore John has a son.
(Invalid. He might have a daughter instead).
These simple logical rules will be crucial to what follows.
Now let’s apply this to the Relativity/Eclipse observation.
5) If Relativity Theory is true, then in an
eclipse the light from the star
will appear at Point X, to the exclusion of all other possible
In fact the light from the star appears at point X, as predicted.
Therefore, The Theory of Relativity is confirmed.
There is a great deal wrong with this simple example, beginning with the
fact that it commits the fallacy of affirming the consequent (4). So if
relativity theory (an antecedent) predicts the appearance of a star at Point
X, and that prediction is subsequently confirmed by observation (a
consequent), how can we trust that alleged "confirmation" if the procedure
is logically invalid? We do so by acknowledging that there might be other
explanations, and then proceed to eliminate these rivals. Also the precision
of the prediction can render the plausibility of alternative explanations to
be extremely unlikely – though not logically impossible.
In addition, the antecedent (relativity theory in this
case) is never a single assertion. It is always a compound of several
assertions. We will return to this point shortly.
So much for empirical confirmation. What about falsification?
A naive interpretation of the falsifiability principle might go like
6) If Relativity Theory is True, then the light from the star
will appear at point X.
The light does not appear at point X.
Therefore, the theory of Relativity is refuted.
The syllogism is valid (denying the consequent –
(3)). But is it a falsification? Is this how we can describe how
relativity might be false, even if it is in fact true? Not so fast!
A failure to find the star at the predicted Point X (a
consequent), validly denies the
truth of the antecedent. But in scientific observation and inquiry, the
antecedent of the hypothetical syllogism is never a single premise. It is
always a compound made up of numerous assumptions: (A&B&C&D...&N) with "N"
the premise to be tested (e.g. E=MC2). All
it takes to find an entire "conjunctive compound" false, is to falsify just
one of the conjuncts. But which one (or more) is false? Neither the
syllogism nor the experiment will tell you.
In the eclipse experiment, these "conjunctive" assumptions include the
laws of optics, the reliability of the telescope mechanism, the laws of
celestial mechanics, the honest reporting of the observers, etc.
"Replicability" and "experimental control" (altering conditions to
eliminate untested assumptions, for example different observers and
different equipment) all serve to minimize the possibility of an error among
the conjunct assumptions. But in principle, total elimination of the
possibility of error among the "base assumptions" is impossible.
So science is fallible. Who’da thunk it?
However, fallibility is not a weakness of science, it is
strength, which opens science to perpetual advancement.. And the presence of
logical fallacies in scientific method only shows us what we should already
know: induction, the method of empirical science is not pure formal logic.
And why not? For a myriad of reasons. But for a start, let’s return to David Hume.
Induction, as Hume cleverly pointed out, is founded on
circular argument: (a) Inductive method assumes that nature is uniform
(i.e., that the fundamental conditions or nature are constant). And
how do we know that nature is uniform? (b) By induction, of course!
In addition, induction commits the fallacy of generalization, as it
infers from "some" to "all." Newton’s Laws of Motion apply to all moving
bodies, even though all moving bodies have not been individually observed.
And Gray’s Anatomy describes all human bodies, even though (fortunately) not
all human bodies have been examined. Even so the surgeon confidently cuts
open the body of the patient on the table, fully expecting to find the vital
organs to be where Gray’s anatomy says they will be.
Generalization to all cases from individual confirming cases is just one
of many inductive strategies. For more, Google "Mill’s Methods of
"So you have shown us that the falsifiability principle is logically
flawed. Why then keep it?"
We should keep falsifiability as a valuable tool of analysis – an
"heuristic device" as philosophers like to call it. When encountering a
startling claim, it may be helpful to ask: "But what would it be like for
your assertion to be false?" And if you can’t answer that -- if your
assertion is true for all possible worlds -- then just what are you
telling me about the world we live in?
"So why trust science at all if, as you say, it is shot through with
First of all, empirical science, qua empirical, is not an exercise
in formal deductive logic. Scrupulously formal logic, because it is devoid
of empirical reference, tells us nothing about the real world. In
other words, formal logic is about "Ps" and Qs" referring to nothing in
particular. It is not about fathers, sons and daughters, etc.
These familial references cited above "interpret" the hypothetical syllogism.
They do not prove validity. (For that, pick up a elementary
logic text, and look up "Truth Tables"). And yet, if formal logic is to be
applied to the "real" (empirical) world, those non-referential "Ps" and "Qs"
("the premises") must be given empirical content, which is to say, they must
be fact-claims. And fact claims cannot be derived from "pure logic."
Enter inductive method.
not to deny that formal logic is an indispensable instrument in the
toolbox of science. In fact, without formal logic (as advanced mathematics) the
confirmation of E=mc2 by way of predicting
an observed Point X in the eclipse experiment would be impossible, as would,
for that matter, Einstein’s derivation of E=mc2.
Empirical science is not "illogical," it is "extra-logical" a methodology
designed, unlike formal logic (however in conjunction with formal logic), to yield information about the natural
world. (See "Hypothetico-Deductive Method").
Why trust science? The pragmatist has the final word:
works. As noted in the essay that prompted this response:
[We all] affirm science every time [we] boot up a computer, start
a car or make a phone call. These everyday activities take place
only through the successful application of thousands of scientific
laws and theories. When the evangelical preacher stands before a TV
camera to denounce evolution, or Donald Trump to debunk global
warming as "unsound science," they both know that the device that is
pointing at them will send their image and words to millions "out
there." Thus they implicitly affirm the validity of physics,
chemistry, advanced mathematics and computer science, even as they
deny biology and atmospheric science.
If any of the thousands of natural laws proven by
science and applied to these devices were even slightly different than
what they have been discovered to be (i.e., a falsification), we could
not boot up our computers or start our cars.