Verification

What it is

The verification principle holds that a statement is meaningful only if there is some possible observation that would count for or against it. Statements failing the test are not false; they are empty — grammatical sentences that make no claim.

Applied wholesale it was a demolition programme, aimed at metaphysics, theology and much of ethics. Applied as a device to a particular claim, it is the plain and useful demand to say what would show you wrong.

How it works

Take the claim. Ask what would be observed if it were true and what would be observed if it were false. If the two are the same, the claim is doing no work. Say so, rather than arguing about whether it is true.

As a device it is applied to somebody else's assertion, and the answer to the question is theirs to supply.

How it is applied

1. Take the claim as stated
2. Ask what would be observed if it were true
3. Ask what would be observed if it were false
4. If the two answers are identical, the claim is empty rather than unproven

What it is good for

Filtering claims that cannot be assessed from claims that merely have not been. It is a good habit in procurement, in policy, and in reading anyone's marketing.

Where it fails

It cannot pass its own test, and this is fatal rather than embarrassing. No observation would show the verification principle itself true or false, so by its own criterion it is meaningless. The Circle knew this and never resolved it.

It also could not be formulated tightly enough. Every precise version either ruled out ordinary scientific laws, which are universal and so never conclusively verified, or was loose enough to let the metaphysics back in. Hempel documented failure after failure through the 1950s.

And it treats meaning as the issue when the issue is usually evidence. A claim nobody can test may still be perfectly meaningful and simply unsupported, which is a more modest and more defensible thing to say.

Common misconceptions

That it is the same as falsifiability. Popper's criterion distinguishes science from non-science and explicitly allows unfalsifiable statements to be meaningful; the verification principle denied them meaning at all, and Popper spent decades objecting to being grouped with the Circle.

Where it came from

The Vienna Circle from the late 1920s, given its most aggressive English statement in Ayer's Language, Truth and Logic in 1936, written when he was twenty-five.

What became of it

Abandoned as a criterion of meaning by about 1960, after repeated failures to state it precisely. Ayer said late in life that its main defect was that nearly all of it was false.

Lasting influence

It shaped a generation of philosophy of science, made the demand for testability standard, and produced by its failure much of what came after it.

Why it still matters

Dead as a theory of meaning, alive and useful as a question to ask.

Put another way

A sieve with a mesh so fine it kept nothing, including itself.

Texts

Where to start

Ayer's first chapter, then Hempel's Problems and Changes in the Empiricist Criterion of Meaning, which is the record of the failures.

The surprising bit

The principle designed to eliminate metaphysics could not survive its own application, and its most famous defender agreed in an interview that it was mostly wrong.

In their own words

Who held it

Carl Hempel

Connections

Influenced

Debunking explanation

Parallel to

The open question

The verdict

A failed theory of meaning that left behind an excellent habit.

Sources

• Stanford Encyclopedia of Philosophy: Vienna Circle