PM5312: Against Logical positivism

Logical positivism is a school of philosophy that was popular in the early-to-mid 20th century. The basic beliefs of logical positivism can be summed up as follows: "All meaningful statements about the world, are either mere definitions, or else there must exist at least in principle a procedure which could verify their truth".

What this basically meant, is that logical positivists believed that for a claim about the world to be meaningful, we must have some way to test if its true. If there is no possible experiment or observation we could perform to test for its truth, the claim is meaningless. Note that they were only concerned about possibility in principle, not possibility in practice. There are many claims about the universe which we lack the means to test at present, and many we may never be able to test. But, from a logical positivist viewpoint, so long as a claim was testable in principle, it was meaningful, even if it could not be tested in practice.

Logical positivists believed that much of traditional philosophy was meaningless and useless; in their minds, philosophy existed to serve the needs of science, to put science on a sure footing. They saw traditional philosophy as a linguistic muddle, nothing more than empty word games, and saw it as their task to dispel them.

Application to religion

Logicial positivists believe that most traditional theological language was meaningless, since there was no test that could be performed to determine if it was true. For example, consider the claim "God is a perfectly simple substance". Logical positivists argued that, since there was no possible test to determine if that claim was true, the claim was meaningless. As a result, many logical positivists embraced a particular form of atheism - to them, the statement "God exists" was totally meaningless, as meaningless as a line from Lewis Caroll's poem Jabberwocky.

However, many religious claims can meet the logical positivist's critera. Consider the claim "There is a life after death". This claim can be tested, by dying - and, since we all shall die one day, we all shall test it. Thus, that claim is meaningful. Similarly, claims about God can be tested by personal experience of God, either in this life or the next, and hence are meaningful. The abstract faith of certain theologians may well be meaningless, but the simpler faith of the average believer does not have this issue.

And, the question remains - why should anyone accept the logical positivist's theory of meaningfulness? If their theory is wrong, then even the most abstract of traditional theology can survive.

Application to ethics

Logicial positivists rejected the idea of objective ethics. To them, a statement "murder is wrong" cannot be cognitively meaningful - it more than a mere defintion, but there is no procedure we can perform to test if it is true. The major logical positivist approach to ethics is emotivism - ethical claims do not have meaning as factual statements do, but they rather serve to express the approval or disapproval of the speaker. According to this theory, "murder is wrong" is a way of expressing a dislike for murder, and nothing more. This is in contrast to what most people believe - that when they say "murder is wrong", they are doing more than just expressing their emotional attitude towards murder - they are actually claiming that there is some central aspect of reality which in an objective sense is opposed to murder.

However, again, logical positivism only succeeds in disproving the objectivity of ethics if the logical positivist's criterion of meaning is correct.


Up until the 1960s, logical positivism could claim to be the most popular school of philosophy in the English speaking world. Yet today, it has very few adherents left. What happened?

It turns out that logical positivism is self-refuting. Consider its fundamental claim "All meaningful statements about the world, are either mere definitions, or else there must exist at least in principle a procedure which could verify their truth". Is that a mere definition of "meaning"? If it is, then logical positivists are certainly free to define the word "meaning" as they want; but no else has to adopt their definition of the word. So, if logical positivism is just an idiosyncratic definition of the word "meaning", it is rather pointless. To be a position worthy of serious consideration, logical positivism must be more than a mere arbitrary definition of a word - it must tell us in some deeper sense what meaning actually is. And yet, if it is not a mere definition, then by its own terms there must exist a procedure which could verify the truth of logical positivism. But what would such procedure be? What test, observation or experiment could one perform to determine the truth of logical positivism? There isn't one. Hence, logical positivism defeats itself.

That is not to say that there are not many philosophers today which are motivated by the same basic perspective which motivated the logical positivists. But no serious philosophers find their simple solutions satisfying, the holes are too gaping and obvious. Logical positivism also tends to be popular with populist advocates of atheism, many of whom do not realise that the world of academic philosophy moved on from logical positivism many decades ago.