Did the denial of human emotion lead to the death of logical positivism?
Logical positivism does not deny human emotion. It simply reassigns its role. Ethical, aesthetic, or religious judgments, for example, fulfill the role of expressing or eliciting emotion - and not, emphatically not, of truth-bearing. Since ethical, aesthetic, and religious judgments occur and since, equally definitely for logical positivists, they cannot be truth-bearers since they are incapable of verification, they are reduced to an emotional function.
This is clear from AJ Ayer's Language, Truth, and Logic, 1936, ch.6.
I am not endorsing logical positivism, only explaining it and setting out how it regards the emotions - those, at least, relevant to ethical, aesthetic, and religious judgment.
Logical Positivism did not fail because it denied human emotion. LP failed because it tried to reduce the concept of meaning to the process of verification, and it became increasingly clear that this was an impossible task (as the later Wittgenstein, among other, pointed out quite clearly). Logical Positivists would look at a scientific proposition — such as the laws of gravity — and note that such theories are meaningful precisely because they can be used functionally in ways that verify them. They wanted to extend that kind of apparent rigor to philosophy more broadly put, and at the same time restrict philosophy more broadly put to questions that could respond fruitfully to that kind of verification. But they could never solve what later came to be known as the demarcation problem: how to simultaneously retain those things they thought should be part of philosophy and exclude those things they thought should not be part of philosophy. The result was an assortment of conflicts and paradoxes that fragmented the movement.
The issue with emotions was an outgrowth of this thinking, not the root of it. Subjective experience (including emotions) is in many ways the converse of metaphysical propositions. One cannot verify a feeling about something, and so from the LP perspective feelings are not proper subjects of philosophical analysis.
Everybody knows nowadays that logical positivism is dead. But nobody seems to suspect that there may be a question to be asked here—the question “Who is responsible?” or, rather, the question “Who has done it?”. (Passmore’s excellent historical article [note 110] does not raise this question.) I fear that I must admit responsibility. Yet I did not do it on purpose: my sole intention was to point out what seemed to me a number of fundamental mistakes. Passmore correctly ascribes the dissolution of logical positivism to insuperable internal difficulties. Most of these difficulties had been pointed out in my lectures and discussions, and especially in my Logik der Forschung. Some members of the Circle were impressed by the need to make changes. Thus the seeds were sown. They led, in the course of many years, to the disintegration of the Circle’s tenets.
This is from the famous chapter "Who killed logical positivism" (17) of Karl Popper’s autobiography, The Unended Quest. The motto for it is from John Passmore’s article “Logical Positivism” in Encyclopedia of Philosophy, ed. by Paul Edwards, Vol. V, p. 57: "Logical positivism, then, is dead, or as dead as a philosophical movement ever becomes."
Karl Popper refuted logical positivism in "The Logic of Scientific Discovery" (LScD).
One problem with the logical positivist position was that the positivists wanted to get rid of metaphysics in favour of science, but their proposed way to distinguishing between them was useless. They wanted to say science consisted of verifiable statements, but an experimental observation doesn't show that a scientific theory is true since any set of observations is compatible with an infinite set of theories. So their proposed criterion of demarcation between science and metaphysics would class every scientific theory ever invented as metaphysics. See LScD Chapter 1, Section 4.
The positivists usually took the position that they could work out what constitutes science by observing scientists and using their observations to work out what counts as science. This position has a couple of problems. First, it will tend to entrench the positions taken by those who are deemed to be scientists regardless of whether their positions can stand up to criticism. Second, it doesn't provide any means of deciding who counts as a scientist. See LScD chapter 2, Sections 9 and 10
Several good answers here. As Geoffrey Thomas points out, LP doesn't "deny" human emotion. It simply tries to remove emotion ("emotion" is used here in the most general sense of the word - i.e. including questions of ethics, values, faith, etc...) from the process of elaborating philosophical statements and results.
I would like to point out though, that some sources consider W.V.O Quine "The Destroyer of Logical Positivism" (paradoxically he is also known as the last logical positivist).
From this point of view, it is neither Karl Popper's views on verfication vs. falsification, and on metaphysics, nor the seeming inconsistency of the verification principle, that brought down Logical Positivism. Several members of the Vienna circle tried to deal with those challenges.
It was Quine's dissolution of the Analytic/Synthetic distinction which doomed the LP program. Quine showed that no matter how hard we try, we cannot separate empirical statements from theoretical constructs.
A purely empirical statement is impossible, since there will always be some theoretical assumptions being made when trying to describe empirical facts.
Conversely, all statements of logic and ideas must rely on definitions, and definitions cannot be always abstract, sooner or later they must be tied to some real world experience or document. (Consider trying to define the number "2" - no matter how hard you try, eventually you will have to simply point to a real world example or document).
This pretty much made LP's separation of statements into either empirical statements or logical statements impossible, and was the true nail in the coffin of LP.
Logical positivism was an approach to philosophy with aspirations to new heights of strictness and rigor. Most famously, it initially endorsed the "verification principle," which states that all meaningful statements must be either based on empirical evidence, or be "truths of logic" (or a combination of the two). However, the verification principle itself is self-defeating, since it itself is neither based on empirical evidence nor is it a truth of logic. Therefore, the verification principle would technically have to judge itself as meaningless.
As with other ambitious analytic projects, such as Russell's attempt to reduce mathematics to logic (proved fatally paradoxical by Godel), logical positivism was influential and arguably productive, but ultimately unsupportable under its own terms, and doomed by the impossibility of its ambitions. This was the proximate cause of its demise.
It's possible to speculate that, in the larger picture, it was too much in thrall to visions of mechanical perfection, and too contemptuous of "fuzzy" human characteristics human such as emotion, but it would be difficult to draw a direct connection between that and its infamous failure as a philosophical movement.