review of relevant literatures on the subjects of logical positivism and Falsificationism.


Introduction
            The point at issue here is the question of what demarcates science from what is not science. Logical positivism or logical empiricism[1] proposes that a synthetic proposition is scientific just in case it is, in fact or in principle, empirically verifiable, in which case it is also meaningful. Karl Popper proposes rather than a criterion of meaning, the criterion of falsifiability or refutability. Accordingly, a proposition is scientific just in case it is falsifiable or refutable; “a theory is falsified only if we have accepted basic statements which contradict it.”[2] Our task here is to briefly discuss logical positivism and Popper’s falsificationism. Therefore, this essay would consist largely in a review of relevant literatures on the subjects of logical positivism and Falsificationism.
Logical Positivism: Its Origin and Foremost Exponents
To say that something is real is to say that certain data are observed, that certain facts are the case.[3]

The above formulation captures the logical positivist mindset. For Albert Blumberg and Herbert Feigl, logical positivism is better described as a “union of empiricism and a sound theory of logic.”[4] Logical Positivism originated in the 1920s with the coming together of a group of scientists, logicians and physicists. They paid much attention to logic, mathematics and the linguistic characteristic of classical philosophical problems.[5] This is such that it can be comfortably stated that:
Logical Positivismis a theory in Epistemology and Logic that developed out of Positivism and the early Analytic Philosophy movement, and which campaigned for a systematic reduction of all human knowledge to logical and scientific foundations. Thus, a statement is meaningful only if it is either purely formal (essentially, mathematics and logic) or capable of empirical verification.[6]
In addition, it seems plausible to corroborate the assertion of Blumberg and Feigl when they aver that:
Logical positivism retains the fundamental principle of empiricism but, profiting by the brilliant work of Poincare and Einstein in the foundations of physics and Frege and Russell in the foundations of mathematics, feels it has attained in most essentials a unified theory of knowledge in which neither logical nor empirical factors are neglected.[7]

This group of scientists, logicians and physicists later came to be known as the Vienna Circle, having been formed in Vienna, Austria.[8] In fact, Logical positivism is seen as the most influential philosophy of science of the 20 century.[9] Though it has been abandoned by most philosophers of science, its’ impact is still felt in other fields of study.[10]
Furthermore, this school of thought thrives on the empirical, positivist, scientific and logical presuppositions and conclusions that:
All knowledge, with the exception of the analytic truths of mathematics and logic, is derived from experience; Metaphysical claims are meaningless since they cannot be verified empirically; the methods of scientific demonstration are the only way to true knowledge; Logical construction plays an important role in relating fundamental data to objects of scientific theories of higher order.[11]
Understandably, Bertrand Russell avows that:
A philosopher is a logical positivist if he holds that there is no special way of knowing that is peculiar to philosophy, but that questions of fact can only be decided by the empirical methods of science, while questions that can be decided without appeal to experience are either mathematical or linguistic.[12]

Some of the earliest members of the logical positivist school are Schlick, Hans Hahn, a mathematician, Philipp Frank, a physicist, Otto Neurath, a social scientist, Olga Hahn-Neurath, a mathematician, Viktor Kraft, a philosopher, Theodor Radacovic and Gustav Bergmann, both mathematicians, the philosopher and logician Rudolf Carnap, Schlick's students to include Friedrich Waismann, Herbert Feigl and Marcel Natkin, Hahn's students, to include Karl Menger and Kurt Gödel, just to mention a few.[13] A. J. Ayer and Hans Reichenbach are known to have introduced logical positivism into England and Berlin respectively.[14]
The Canon of Logical Positivism: A Simple Outline
The avowed commitment of logical positivism is argued to be the decontamination and sanitization of language.[15] With them then, philosophy was assigned the character of clarifying language.[16] Little wonder Russell would agree with Rudolf Carnap that the clarification of language is necessary for the solution of the many problems of philosophy.[17] Logical positivism is seen therefore as philosophy coming to rescue humanity from the fetters of bad science and especially, metaphysics.[18] Accordingly, David Weissman describes the logical positivist attitude such that “metaphysics could only be a corrupting confusion. Cutting it off, like a gangrenous foot, would be an exercise in honorable self-denial.”[19] By “basing its assertions upon recent developments in factual and formal sciences,” logical positivism “holds that factual (empirical) propositions though synthetic are a posteriori, and that logical and mathematical propositions though a priori are analytic.”[20] Mathematical and logical propositions lack empirical content and being simply analytic, they are tautological, in that they do not tell us anything new.[21] Synthetic propositions on the other hand, are factual and report the empirical. They carry content; can be true or false when tested against experience. For the logical positivists then:
The synthetic statements of the empirical sciences…were held to be cognitively meaningful if and only if they were empirically testable in some sense. They derived their justification as knowledge claims from successful tests.[22]
Consequently, metaphysical assertions would be ultimately meaningless since they are neither synthetic nor analytic. Same goes for the assertions of normative ethics. The propositions of both metaphysics and normative ethics are not verifiable. That is, there are no conditions upon which they can be proven to be true or false.
More so, the logical positivist conception of knowledge is that knowledge is “the communicable.”[23] Moreover, “what knowledge communicates is structure; this it does by means of a symbolism or language.”[24] Language here is instrumental for the communication of facts. This communication is made possible by the use of selected language rules such that the “relations of words in the proposition represent the relations of elements in the fact.”[25] Accordingly, this reasoning presumes an isomorphism between language and fact and the claim is that this isomorphism is inexpressible in any system of language. Wittgenstein for example is said to have noted that this isomorphism between language and fact is simply self evident.[26] Russell puts it this way: “He (Wittgenstein) had maintained that the form of a sentence can only be shown, not stated.”[27]
In the logical positivist view then, what we should concern ourselves with are the sorts of things that are communicable. The sorts of things that are communicable are expressed in a system of language. Communication is done through language and language expresses facts and those things are factual which are empirical and experiential.[28] The factual is also the meaningful. Thus,
To know the meaning of a proposition is to know what must be the case if the proposition is true. The meaning of a complex proposition is revealed when we analyze it into its component atomic propositions. The meaning or sense (Sinn) of an atomic proposition is the "being-the-case" or the "not-being-the-case" of the fact which it expresses. The meaning (Bedeutung) of a complex word or concept is given by explicit definition; that of a simple word or name by pointing to what it stands for in experience.[29] 

It is based on this, the criterion of meaning that the logical positivists distinguish between science and non science. In order to know the meaning of a proposition, we ask, under what conditions can this proposition be true? These conditions constitute the procedure of verification through experience. A proposition is true just in case what it asserts is really the case and false on the contrary. The truth or falsity of a proposition is ascertained by comparing the said proposition with reality/experience. If experiential conditions cannot be established, whether in practice or in principle, then the proposition is meaningless; if they can be established, then the statement is meaningful.
Following from this, scientific propositions are meaningful because they can be verified – there are established conditions upon which they can be proven to be true, whereas, non scientific propositions are meaningless because they cannot be verified. Blumberg and Feigl are quick to add that “the meaningfulness of a proposition shows itself when we ask whether it is verifiable.”[30]
It seems that science would depend more on reported facts from experience to substantiate clearly logical claims deductively arrived at and embellished in a given theory.[31] We have noted earlier that the logical positivists assumed isomorphy between syntax and matter of fact. Indeed, this is the basis of their acceptance of the fact that true knowledge is based on experience and analytic/ tautologous propositions. Consequently, there is a distinction made between observational and theoretical terms; between synthetic and analytic statements; between theoretical axioms and rules of correspondence; the deductive nature of scientific theories. Thus:
Rules of correspondence give an empirical meaning to theoretical terms and are analytic, while theoretical axioms express the observational portion of the theory and are synthetic. A theory must be a deductive system; otherwise, a formal distinction between the various kinds of sentences and terms is impossible.[32]

But we might want to ask, what is the status of observational language? Are all synthetic propositions therefore empirically verifiable? What language is adequate for the formulation scientific theories?  Undeniably, the language of observation is, for the logical positivists, as also for other philosophers of science. For any theory to be verifiable it must be such that it can be observed inter-subjectively.[33] It is curious however, how John Loose notes in his Historical Introduction to the Philosophy of Science how George Berkeley critiqued Newton’s system of thought noting as he did that Newton talks about forces as if they are more than terms in equation. Forces in mechanics are analogous to epicycles in astronomy; the mathematical formulations are useful in calculating the motions of bodies. Berkeley says that it is therefore a mistake to attribute to those formulations real existences in the world.[34] So one may ask, what does the scientist observe when Berkeley is watching him?
The Supposed Impact of Logical Positivism
As earlier stated, with their insistence on the criterion of meaning or cognitive significance[35] based on verifiability, the logical positivists intended to singlehandedly stage manage the death of metaphysics and normative ethics while underpinning true knowledge, as we have noted, with the empirical, scientific thrust. Indeed, if the criterion of meaning is applied to the systems of metaphysics and normative ethics, they would not survive. Metaphysics dies with the application of the criterion of meaning because “since their propositions are admittedly incapable of empirical verification, they have no meaning as knowledge.”[36] And normative ethics faces the same fate because “experience reveals what is, never what ought to be.”[37] However, John Passmore has some candid opinion for the metaphysician as he notes that the logical positivist criterion of meaning undercuts logical positivism itself. Thus:
The proposition that ‘The meaning of a proposition is the method of its verification’ is not a scientific proposition. Should it therefore be rejected as meaningless? Faced with this difficulty, the logical positivists argued that it ought to be read not as a statement but as a proposal, a recommendation that propositions should not be accepted as meaningful unless they are verifiable… the metaphysician could escape their criticism simply by refusing to accept their recommendations.[38]

It is instructive to note that A. J. Ayer in his Language, Truth, and Logic argues that all ethical and aesthetic judgments such as saying that ‘this is bad’ or ‘that is beautiful’, are mere emotional expressions that cannot be attributed any objectively valid judgment; rather, these can be scientifically treated by ascertaining the general causes and milieu from which these judgments are formed.[39]
Criticism of Logical Positivism

            Concerning the verifiability principle, Bertrand Russell vehemently observes with certain suspicion:
That a proposition is verifiable is itself not verifiable. This is because to state that all the future consequences of a general proposition are true is itself a general proposition of which the instances cannot be enumerated, and no general proposition can be established on purely empirical evidence except one applying to a list of particulars all of which have been observed.[40]

Moreover, the very criterion of meaning or cognitive significance espoused by logical positivists is the nemesis of logical positivism. It has been widely argued against them that empirical science, which they sought to set free from the entanglements of the high sounding language of metaphysics, dies with the verifiability principle. As indeed, the scientific method advanced by the logical positivists stressed the meaningfulness of propositions, it left the propositions of science vulnerable to the same criterion. One could not agree more with Bruce Caldwell in his interpretation of Popper’s critique. Thus for Popper,
"Unicorns exist." Th(is) sentence can be verified by finding a unicorn. But it cannot be falsified, even if it is false: The failure to find a unicorn does not establish that none exists. If verifiability is used as the demarcation criterion, the statement "unicorns exist" would have to be considered a part of science.[41]
Again, since scientific propositions are of universal form: All Bs are x, critics argue that such propositions are not empirically verifiable. Earlier, David Hume in his critique of induction had noted the invalidity of universal statements, and consequently, their lack of empirical significance or meaning. Thus,
It was Hume who first pointed out, and with all his customary lucidity, that from no finite number of observations, however large, could any unrestrictedly general conclusion be drawn that would be defensible in logic…. their unrestricted generality makes it permanently impossible to verify them empirically, by no matter how many observations—trillions, zillions, any number anyone cares to name. So, said Popper, from the Verification Principle it follows that scientific laws are meaningless statements, and are empty of informational content. The Verification Principle rules out all scientific laws, and therefore the whole of science.[42]

Seeing that this principle of verifiability is self destruct to logical positivism modifications were advanced by some logical positivists leading to the lessening of the hold on strict verification via experience. This is clearly evident in Rudolf Carnap, an intransigent adherent of the logical positivist tradition.  It does then follow as Thomas Uebel puts it that
While Carnap's focus on the reduction of descriptive terms allows for the conclusive verification of some statements, it must be noted that his criterion also allowed universally quantified statements to be meaningful, provided they were syntactically and terminologically correct.[43]

Subsequently, the verifiability criterion was reduced to confirmability or testability with Carnap. Thus, a proposition should at least be testable for it to pass as scientific. Thomas Kuhn takes logical positivism to task on this confirmability principle, arguing as George Reisch notes that Kuhn denied “the notion that theories can simply be judged according to how well they fit the facts, or, for logical empiricism, according to their measure of empirical confirmation.”[44] However, Reisch posits that Carnap’s contribution to the philosophy of science is identical to Kuhn’s and does not see much reason why Kuhn could stand up against logical positivism which Carnap seem to ably represent.[45] It seems pertinent at this point to point out Karl Popper’s take on the demarcation problem.
Karl Raimund Popper: On the “Problem of Demarcation”[46]
Karl R. Popper is considered one of the most eminent philosophers of science of the twentieth century. He vehemently opposed the Baconian observationalist-inductivist method of science, appraised the logical positivist criterion of verifiability and proposed the falsifiability criterion demarcating between science and non science.[47] His main concern in the philosophy of science is evidently the demarcation problem; hence he notes in his The Logic of Scientific Discovery that:
My business, as I see it, is not to bring about the overthrow of metaphysics. It is, rather, to formulate a suitable characterization of empirical science, or to define the concepts of ‘empirical science’ and ‘metaphysics’ in such a way that we shall be able to say of a given system of statements whether or not its closer study is the concern of empirical science.[48]

This confessed philosopher of science denied that verifiability is a better principle for demarcation since certain propositions could be verified but not falsified. Moreover,
Popper shared the logical positivist concern with demarcation, but he did not accept the meaningful-meaningless dichotomy. His demarcation criterion separates the scientific from the nonscientific, or metaphysical. (Thus for Popper some statements can be nonscientific but still meaningful.)[49]
Furthermore, James Ladyman observes that one of the important reasons for acquiring the method of scientific theory is the ability to determine the justification of scientific knowledge claims, as well as distinguishing genuine scientific theories from those that either claim or seem to be scientific.[50] Therefore, the grounds and criteria through which science is demarcated from non-science is referred to as ‘falsificationism’, which is Karl Popper’s method of scientific theory.[51] It is expedient to note that theory was more accepted amongst the scientists than amongst philosophers.[52] According to Ladyman, Popper is bothered by the idea that vague theories are acclaimed scientific just because they attain popular confirmation. He thus argues that theories such as these are most likely to be false science because their vagueness gives them a great explanatory power which makes them to appear scientific. Furthermore, Popper asserts that the confirmation of any theory would only be credible if its prediction of phenomena occurrence entails risk that would ultimately falsify such theory in its failing.[53]
In addition, James Ladyman is quick to add that “science does not depend on induction at all”[54] because induction does not justify scientific knowledge. Moreover, the greatest problem of induction is that it takes just one contrary instance to falsify a generalization. For example, the proposition- “All lions are brave”, only requires a single case of a lion that is not brave to falsify it. Popper therefore argues that only theories that are falsifiable by experience can be termed scientific; for, “it is falsification and not confirmation that is at the heart of the scientific method.”[55] According to Popper, the empirical contents of theories are authentically measured if such theories could be categorized according to their degrees of falsifiability, because it enables theories to make predictions on various observable occurrences.[56]
Furthermore, A. F. Chalmers attempts to tamper the enthusiasm of Popper and his falsification criterion noting that that a hypothesis should not just be falsifiable but more falsifiable than the one for which it is offered as a replacement. This perspective Chalmers calls sophisticated falsificationism.[57]
The Limitations of Falsificationism
First, falsificationism is undermined by the fact that observation statements are theory-dependent and fallible. Falsificationism argues that if true observation statements are given, then it is possible to logically deduce from them the falsity of some universal statements; whereas it is not possible to deduce from them the truth of any universal statements. Chalmers argues that this is an unexceptional point based on the assumption that perfectly secure observation statements are available. However, this is not the case since all observation statements are fallible. Thus, if a universal statement constituting a theory or part of a theory clashes with some observation statement, it may be the observation statement that is faulty. Hence, a fallible observation statement might be rejected and the fallible theory with which it clashes retained. So, conclusive falsifications of theories are impossible.[58]
Secondly, the statement “All swans are white” is certainly falsified if an instance of a non-white swan can be established. However, simplified illustrations of the logic of a falsification such as these disguise a serious difficulty for falsificationalism that arises from the complexity of any realistic test situation. A realistic scientific theory consists of a complex of universal statements rather than a single statement. A theory that is to be experimentally tested requires more than those statements that constitute the theory under test. The theory will need to be augmented by auxiliary assumptions, such as laws and theories governing the use of any instruments used.  More so, to deduce some prediction, the validity will be necessary to add initial conditions. If a prediction that follows from a number of premises turns out to be false, then all that the logic of the situation permits us to conclude is that at least one of the premises must be false. It does not enable us to identify the faulty premise. Thus, a theory cannot be conclusively falsified, because the possibility that some part of the complex test situation other than the theory under test, is responsible for an erroneous prediction cannot be excluded.[59]
In addition, historically, if the falsificationism methodology had been strictly adhered to by scientist then those theories generally regarded as being among the best examples of scientific theories would never have been developed because they would have been rejected in their infancy. Chalmers argues that given any classic scientific theory, although it is possible to find observational claims that were generally accepted at the time and were considered to be inconsistent with the theory; those theories were not rejected. For instance, when Newton’s gravitational theory was falsified by observations of the moon’s orbit, scientists did not abandon it. It turned out that it was never possible to explain away this falsification in a way that protected Newton’s theory.[60] Furthermore, in 1543, Copernicus revolutionized astronomy. In contrast to Aristotelian and Ptolemaic system, Copernicus posits that the earth is not stationary at the centre of the universe but revolves around the sun along with the planets. With this emergence, neither the inductivists nor the falsificationsts give an account of science that is compatible with it. Early formulations of the new theory, involving imperfectly formulated novel conceptions, were persevered with and developed in spite of apparent falsifications.[61]
Conclusion
            We have briefly surveyed the intellectual contributions of the logical positivists and the falsificationist criterion of Karl Popper in the demarcation of science from non science and pseudo science. We have noted that the logical positivists offer the verifiability criterion of meaning, thus the meaning of a proposition is its method of verification. However, we did try to show, with some literatures, how this claim is self undercutting; for the proposition that the meaning of a proposition is its method of verification is itself not verifiable. Besides, we noted the difficulty of verifying universal statements, upon which, unfortunately, scientific theories are built. More so, we tried to highlight Karl Popper’s criterion of falsifiability for science, consequent upon which a proposition is scientific if it is falsifiable. We noted, nevertheless, that falsification is not without its own drawbacks. It could seem then to go without saying that the logical positivists and Popper have really left a legacy in the development of thought. Notwithstanding, their efforts have not been completely irrefutable. Indeed, we noted earlier that at some point, the logical positivist saw their verifiability principle as merely a recommendation. Karl Popper himself notes that “I do not demand that every scientific statement must have in fact been tested before it is accepted”[62] and calls his principle of falsifiability as proposal.[63]
Bibliography

Books
Ayer, A. J. Language, Truth, and Logic. New York: Dover Publications, 1952.

Chalmers, A.F. What is this thing Called Science? Buckingham: Open University Press, 1990.

Ladyman, James. Understanding Philosophy of Science. New York: Routledge, 2002.

Lawhead, William F. The Voyage of Discovery. Belmont: Wadworth Group, 2002.

Loose, John. Historical Introduction to Philosophy of Science. New York; Oxford University
press, 1972.

Popper, Karl R. The Logic of Scientific Discovery. London: Hutchinson & Co. Ltd, 1975.

Encyclopedias
Nickles, Thomas “Problem of Demarcation” The Philosophy of Science, An Encyclopedia
Sahotra Sarkar and Jessica Pfeifer (eds.). New York: Routledge, 2006. s.v.

Passmore, John “Logical Positivism” The Encyclopedia of Philosophy, vols 5 & 6, Paul Edwards
(ed.). New York: Macmillan Publishing Co. Inc & The Free Press, 1967. s.v.

Thornton, Stephen P. “Karl Raimund Popper” The Philosophy of Science, An Encyclopedia
Sahotra Sarkar and Jessica Pfeifer (eds.). New York: Routledge, 2006. s.v.

Journals
Blumberg, Albert E. and Feigl, Herbert “Logical Positivism” The Journal of Philosophy, Vol.
28, No. 11 (May 21, 1931), pp. 281-296

Caldwell, Bruce J. “Clarifying Popper” Journal of Economic Literature, Vol. 29, No. 1 (Mar.,
1991), pp.1-33

Hempel, Carl G. “Problems and Changes in the Empiricist Criterion of Meaning” Revue
Internationale de Philosophie,Vol. 4, No. 11 (Janvier 1950), pp. 41-63.

Reisch, George “Did Kuhn Kill Logical Empiricism?” Philosophy of Science, Vol. 58, No. 2
(Jun., 1991), pp. 264-277

Russell, Bertrand “Logical Positivism” Revue Internationale de Philosophie, Vol. 4, No. 11
(Janvier 1950), pp. 3-19

Weissman, David “Logical Positivism: A Retrospective” The Journal of Philosophy, Vol. 88,
No. 10, (Oct., 1991), pp. 520-521

Internet Materials
Accessed on 12/4/15

“Logical Positivism” http://www.loyno.edu/~folse/logpos.htm Accessed on 14/4/15

Magee, Bryan “The Confessions of a Philosopher” Philosophy Lovers,

Mastin, Luke “Logical Positivism”

Uebel, Thomas, "Vienna Circle", The Stanford Encyclopedia of Philosophy (Spring 2014
Edition), Edward N. Zalta (ed.), <http://plato.stanford.edu/archives/spr2014/entries/vienna-circle/>. Accessed on 10/4/15



[1] Cf. William F. Lawhead, The Voyage of Discovery (Belmont: Wadworth Group, 2002), p.506
[2] Karl R. Popper, The Logic of Scientific Discovery (London: Hutchinson & Co. Ltd, 1975), p.86
[3] Albert E. Blumberg and Herbert Feigl “Logical Positivism” The Journal of Philosophy, vol. 28, no. 11 (May 21, 1931), p.295
[4] Albert E. Blumberg and Herbert Feigl “Logical Positivism” The Journal of Philosophy, p.282
[5] Cf. Bertrand Russell “Logical Positivism” Revue Internationale de Philosophie, vol. 4, no. 11 (Janvier 1950), p.3
[6] Luke Mastin “Logical Positivism” http://www.philosophybasics.com/branch_logical_positivism.html accessed on 8/4/15
[7] Albert E. Blumberg and Herbert Feigl “Logical Positivism” The Journal of Philosophy, p.282
[9] Cf. “Logical positivism” p.303
[10] Cf. “Logical positivism” p.315
[11] “Logical positivism” p.311
[12] Bertrand Russell “Logical Positivism” Revue Internationale de Philosophie, vol. 4, no. 11 (Janvier 1950), p.3
[13] Cf. Uebel, Thomas, "Vienna Circle", The Stanford Encyclopedia of Philosophy (Spring 2014 Edition), Edward N. Zalta (ed.), http://plato.stanford.edu/archives/spr2014/entries/vienna-circle/ accessed on 10/4/15
[14] Cf. William F. Lawhead, The Voyage of Discovery (Belmont: Wadworth Group, 2002), p.506
[15] Cf. Albert E. Blumberg and Herbert Feigl “Logical Positivism” The Journal of Philosophy, p.292
[16] Cf. Uebel, Thomas, "Vienna Circle", The Stanford Encyclopedia of Philosophy
[17] Cf. Bertrand Russell “Logical Positivism” Revue Internationale de Philosophie, pp.6-7
[18] Cf. Bertrand Russell “Logical Positivism” Revue Internationale de Philosophie, p.3 
[19] David Weissman “Logical Positivism: A Retrospective” The Journal of Philosophy, vol. 88, no. 10, (Oct., 1991), p.520
[20]  Albert E. Blumberg and Herbert Feigl “Logical Positivism” The Journal of Philosophy¸ p.282
[21] Cf. Uebel, Thomas, "Vienna Circle", The Stanford Encyclopedia of Philosophy
[22] Uebel, Thomas, "Vienna Circle", The Stanford Encyclopedia of Philosophy 
[23] Albert E. Blumberg and Herbert Feigl “Logical Positivism” The Journal of Philosophy, p.286
[24] Albert E. Blumberg and Herbert Feigl “Logical Positivism” The Journal of Philosophy, p.286
[25] Albert E. Blumberg and Herbert Feigl “Logical Positivism” The Journal of Philosophy, p.287
[26] Cf. Albert E. Blumberg and Herbert Feigl “Logical Positivism” The Journal of Philosophy, p.287
[27] Cf. Bertrand Russell “Logical Positivism” Revue Internationale de Philosophie, p.7
[28] Cf. Bertrand Russell “Logical Positivism” Revue Internationale de Philosophie, p.17
[29] Albert E. Blumberg and Herbert Feigl “Logical Positivism” The Journal of Philosophy, p.287
[30] Albert E. Blumberg and Herbert Feigl “Logical Positivism” The Journal of Philosophy, p.296
[31] “Logical Positivism” http://www.loyno.edu/~folse/logpos.htm accessed on 14/4/15
[32] “Logical Positivism” http://www.loyno.edu/~folse/logpos.htm accessed on 14/4/15
[33] Cf. Karl R. Popper, The Logic of Scientific Discovery (London: Hutchinson & Co. Ltd, 1975), p.47
[34]John Loose, Historical Introduction to Philosophy of Science (New York; Oxford university press, 1972), p.144
[35] Carl G. Hempel corroborates the use of the term “cognitive significance.” See his “Problems and Changes in the Empiricist Criterion of Meaning” Revue Internationale de Philosophie, vol. 4, no. 11 (Janvier 1950), pp. 41-63.
[36] Albert E. Blumberg and Herbert Feigl “Logical Positivism” The Journal of Philosophy, p.293
[37] Albert E. Blumberg and Herbert Feigl “Logical Positivism” The Journal of Philosophy, p.293
[38] John Passmore “Logical Positivism” The Encyclopedia of Philosophy, vols 5 & 6, Paul Edwards (ed) (New York: Macmillan Publishing Co. Inc & The Free Press, 1967), p.55
[39] Cf. A. J. Ayer, Language, Truth, and Logic (New York: Dover Publications, 1952), p. 112-113.
[40] Bertrand Russell “Logical Positivism” Revue Internationale de Philosophie, p.12
[41] Bruce J. Caldwell “Clarifying Popper” Journal of Economic Literature, Vol. 29, No. 1 (Mar., 1991), p.2
[42] Bryan Magee “The Confessions of a Philosopher” Philosophy Lovers, http://www.basicincome.com/bp/whatwasalmost.htm accessed on 12/4/2014.
[43] Uebel, Thomas, "Vienna Circle", The Stanford Encyclopedia of Philosophy
[44] George Reisch “Did Kuhn Kill Logical Empiricism?” Philosophy of Science, vol. 58, no. 2 (Jun., 1991), p.268
[45] Cf. George Reisch “Did Kuhn Kill Logical Empiricism?” Philosophy of Science
[46] This is Karl Raimund Popper’s favored way of characterizing the task of differentiating science from non science. See Thomas Nickles “Problem of Demarcation” The Philosophy of Science, An Encyclopedia Sahotra Sarkar and Jessica Pfeifer (eds.) (New York: Routledge, 2006), pp.188-197 
[47]Cf. Stephen P. Thornton “Karl Raimund Popper” The Philosophy of Science, An Encyclopedia Sahotra Sarkar and Jessica Pfeifer (eds.) (New York: Routledge, 2006), pp.571-572
[48] Karl R. Popper, The Logic of Scientific Discovery (London: Hutchinson & Co. Ltd, 1975), p.37
[49] Bruce J. Caldwell “Clarifying Popper” Journal of Economic Literature, Vol. 29, No. 1 (Mar., 1991), p.2
[50] Cf. James Ladyman, Understanding Philosophy of Science (New York: Routledge, 2002), p. 62
[51] Cf. James Ladyman, Understanding Philosophy of Science, p. 64.
[52] Cf. James Ladyman, Understanding Philosophy of Science, p. 65.
[53] Cf. James Ladyman, Understanding Philosophy of Science, p. 68.
[54] James Ladyman, Understanding Philosophy of Science, p. 69.
[55] James Ladyman, Understanding Philosophy of Science, p. 69.
[56]  Cf. James Ladyman, Understanding Philosophy of Science, 73.
[57] Cf. A.F. Chalmers, What is this thing Called Science? (Buckingham: Open University Press, 1990),  p. 50.
[58] Cf. A.F. Chalmers, What is this thing Called Science? (Buckingham: Open University Press, 1990),  pp. 60-6.
[59] Cf. A.F. Chalmers, What is this thing Called Science? (Buckingham: Open University Press, 1990),  p 64.
[60] Cf. A.F. Chalmers, What is this thing Called Science? (Buckingham: Open University Press, 1990),  p. 66.
[61] Cf. A.F. Chalmers, What is this thing Called Science? (Buckingham: Open University Press, 1990), p.67-74.
[62] Karl R. Popper, The Logic of Scientific Discovery (London: Hutchinson & Co. Ltd, 1975), p.47
[63] Cf. Karl R. Popper, The Logic of Scientific Discovery (London: Hutchinson & Co. Ltd, 1975), p.78

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