What  is logical positivism?

It has been a while since I added an installment in the “Nuts and Bolts” series, where I lay out some of the fundamental ideas and terms used in philosophy (and I’ll do some in theology as well). This time I’m briefly covering the perspective called logical positivism, a point of view with important consequences in science, epistemology, ethics, philosophy of religion and probably a whole lot more.

Logical positivism was primarily an earlier to mid twentieth century movement, arising among a group of philosophers now referred to as The Vienna Circle, but I won’t wade through the history of the movement here. Logical positivism is not a standpoint on what is true and what is not. Instead, it’s a standpoint on what kind of utterances count as real statements that have meaning.

The two criteria through which the logical positivists filtered anything purporting to be a proposition were firstly the analytical truth criterion of meaning and secondly the verifiability criterion of meaning. If a statement is meaningful, it will either be true by definition (i.e. analytically true), or else it will be empirically verifiable. Failing this, a collection of words has no meaning at all and cannot be true or false. A. J. Ayer, perhaps the paradigmatic logical positivist, summed the verificationist position up succinctly.

The criterion which we used to test the genuineness of apparent statements of fact is the criterion of verifiability. We say that a sentence is factually significant to any given person, if, and only if, he knows how to verify the proposition which it purports to express – that is, if he knows what observations would lead him, under certain conditions, to accept the proposition as being true, or reject it as being false. If, on the other hand, the putative proposition is of such a character that the assumption of its truth, or falsehood, is consistent with any assumption whatsoever concerning the nature of his future experience, then, as far he is concerned, it is, if not a tautology, a mere pseudo-proposition. The sentence expressing it may be emotionally significant to him; but it is not literally significant.1

What then of moral claims, such as the claim that “rape is wrong”? It is not analytically true, since “wrongness” is not tied up in the meaning of the word “rape.” If it were, the question “is rape wrong” makes as much sense as asking “is rape rape?” It is clear that a statement like “rape is wrong” is meant to be a synthetic proposition, combining the idea of rape with the idea of wrongness. This means that if the statement is to be meaningful at all, the logical positivists would have had us think, its truth must be verifiable. Since its truth is not verifiable, however, it is not meaningful at all. And in the sense of “verification” intended by Ayer, such claims are not verifiable, since verificationism is concerned with empirical verification.

Similarly, metaphysical claims like claims about whether or not there is a God are rejected by logical positivism – not as false, but as meaningless utterances, since, we are told, “God exists” is not true by definition, nor is it empirically verifiable. I’m going to set aside for now the fact that there are at least some believers in God who think that you can start with empirically verifiable facts and reason to the existence of God.

Perhaps the most striking initial feature of logical positivism is that it is a claim about what statements mean (or fail to mean). When people say that something is morally wrong or that God exists (or that God does not exist), it certainly looks and sounds like they’re saying something that means something, even if they’re wrong.

However there’s a much more important reason that logical positivism did not take hold in the long term.

Logical positivism is, in short, the claim that “In order to be meaningful a statement must be analytically true or empirically verifiable.” All it took was for someone to ask if this claim is a meaningful proposition. If logical positivism is correct, it renders this proposition meaningless, since it is not verifiable, showing that logical positivism was hopelessly self-defeating. The alternative is that the above statement need not be analytically true or verifiable in order to be meaningful, in which case we should deny that this statement is true (because we have just contradicted it). Either way, the prospects for logical positivism were not good. Alan Donagan summed up the simplicity of this controversy as succinctly as anyone: “The Verifiability Principle was no sooner advanced than critics pointed out that, if cognitively meaningful, it is self-refuting.”2 Those who don’t particularly feel like living up to the verificationist principle can simply say “thanks but no thanks.”

If we retreat back from a verificationist criterion of meaning to what might initially sound like something less ambitious such as a verificationist criterion of truth instead, we would get nowhere, since the criterion is the same, and it was the criterion that made the claim problematic. The claim that any proposition must be verifiable in order to be true, in addition to being wildly implausible,3 is still self defeating as it is, once again, not verifiable.

Glenn Peoples

  1. A. J. Ayer, Language, Truth and Logic (London: Penguin Books, 1990, 2nd ed.), 16. []
  2. Alan Donagan, “The Encyclopedia of Philosophy (Review),” The Philosophical Review 79:1 (1970), 87. []
  3. I say that a verificationist criterion of truth is wildly implausible because of the claims that would be automatically deemed false. For example, there is a fact about the last words to go through George Washington’s mind before he died, but if we adopt a verificationist criterion of truth, every possible statement about what those words were would be deemed false (since we cannot verify what the last words actually were), even if the proposed statement was in fact the last to go through George Washington’s mind before he died. []