Language, Truth and Logic
Ayer (A.J.)
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Authors Citing this Book: Ayer (A.J.)


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  1. This book expresses the core theory of Logical Positivism in its more developed form. In short: a factually significant proposition (i.e. a proposition that actually says something about the observable world) must be verifiable or falsifiable at least in principle, by some possible observations which would increase or decrease the probability of the proposition being true. The only other meaningful statements are tautologies, they say the same thing twice: a tautology is true of false in virtue of the definitions of terms used. Or put another way, in analytic language one may say anything they want and make up any definitions with the one condition that one may not contradict oneself. This doctrine (of logical positivism in general) derives from classic empiricism, which asserts that all knowledge of the world must derive solely from sense-data (using our 5 senses) and our human ability to conceptualise and organise such data.
  2. From these claims, Ayer develops the emotivist theory of values and argues that literal assertions about God, of any supernatural entity, or of literally 'good' or 'evil' behaviour are literally senseless (they say nothing at all about the empirical world). Religious and moral languages do, of course, have aesthetic value in so much as they express how we feel about the world.
  3. He also explains how Mathematical reasoning is possible and how Mathematical theories can be described as 'true' - Maths is a form of analytic reasoning so that a Mathematician may say anything he wants and define any symbol however he wants (i.e. lays down axioms and definitions) so long as he does not contradict himself. Theorems can be derived by carefully investigating what is implied by these axioms and definitions.
  4. Language, Truth and Logic is not too long (it can be read in about 6 hours or so) but clearly and systematically develops a coherent account of human logic. Ayer answers many classic problems in Philosophy while at it – problems such as God, monism vs pluralism etc – (which) can often be reduced to meaninglessness. He attempts to answer the problem of whether there is any reason to believe in other minds, through analogy of observable body to unobservable mind, but he himself (in his introduction) admits that he had not resolved the dilemma altogether (e.g. it may still be questioned why other material bodies may behave as humans without experiencing sensations like you yourself do [assuming you yourself have a mind!].)
  5. This work ranks alongside "Russell (Bertrand) - The Problems of Philosophy" and Russell and Whitehead's 'Principles of Mathematics2' as one of the key works of early 20th Century analytic philosophy; crucial to anyone with an interest in Philosophy (or to some extent any Science).

In-Page Footnotes ("Ayer (A.J.) - Language, Truth and Logic")

Footnote 1: Footnote 2:

Pelican, Penguin Books, London; Second Edition (1946, 1986 reprint)

"Ayer (A.J.) - Language, Truth and Logic; Introduction"

Source: Ayer - Language, Truth and Logic, Introduction

Section Headings1
  • 7: The Principle of Verification
  • 21: The ‘A Priori’
  • 24: Propositions about the past and about other minds
  • 26: The Emotive Theory of Values
  • 29: The Nature of Philosophical Analysis

In-Page Footnotes ("Ayer (A.J.) - Language, Truth and Logic; Introduction")

Footnote 1:
  • With page numbers.
  • This is the Introduction to the Second Edition, written 10 years after the first, and responding to the criticism that had been received in the interim. Ayer had changed his views somewhat, though not his fundamental position, but didn’t want to change his “young man’s book” into something else.
  • My view if that Ayer’s approach – like Hume’s famous dictum – is excellent for distinguishing sense from nonsense, but not – in all cases – the meaningful from the meaningless.

"Ayer (A.J.) - Language, Truth and Logic; Preface"

Source: Ayer - Language, Truth and Logic, Preface

Preface To First Edition
  1. The views which are put forward in this treatise derive from the doctrines of Bertrand Russell and Wittgenstein, which are themselves the logical outcome of the empiricism of Berkeley and David Hume. Like Hume, I divide all genuine propositions into two classes: those which, in his terminology, concern 'relations of ideas', and those which concern `matters of fact'. The former class comprises the a priori propositions of logic and pure mathematics, and these I allow to be necessary and certain only because they are analytic. That is, I maintain that the reason why these propositions cannot be confuted in experience is that they do not make any assertion about the empirical world, but simply record our determination to use symbols in a certain fashion. Propositions concerning empirical matters of fact, on the other hand, I hold to be hypotheses, which can be probable but never certain. And in giving an account of the method of their validation I claim also to have explained the nature of truth.
  2. To test whether a sentence expresses a genuine empirical hypothesis, I adopt what may be called a modified verification principle. For I require of an empirical hypothesis, not indeed that it should be conclusively verifiable, but that some possible sense-experience should be relevant to the determination of its truth or falsehood. If a putative proposition fails to satisfy this principle, and is not a tautology, then I hold that it is metaphysical, and that, being metaphysical, it is neither true nor false but literally senseless. It will be found that much of what ordinarily passes for philosophy is metaphysical according to this criterion, and, in particular, that it can not be significantly asserted that there is a non-empirical world of values, or that men have immortal souls, or that there is a transcendent God.
  3. As for the propositions of philosophy themselves, they are held to be linguistically necessary, and so analytic. And with regard to the relationship of philosophy and empirical science, it is, shown that the philosopher is not in a position to furnish speculative truths, which would, as it were, compete with the hypotheses of science, nor yet to pass a priori judgements upon the validity of scientific theories, but that his function is to clarify the propositions of science, by exhibiting their logical relationships, and by defining the symbols which occur in them. Consequently I maintain that there is nothing in the nature of philosophy to warrant the existence of conflicting philosophical `schools'. And I attempt to substantiate this by providing a definitive solution of the problems which have been the chief sources of controversy between philosophers in the past.
  4. The view that philosophizing is an activity of analysis is associated in England with the work of G. E. Moore and his disciples. But while, I have learned a great deal from Professor Moore, I have reason to believe that he and his followers are not prepared to adopt such a thoroughgoing phenomenalism as I do, and that they take a rather different view of the nature of philosophical analysis. The philosophers with whom I am in the closest agreement are those who compose the 'Viennese circle', under the leadership of Moritz Schlick, and are commonly known as logical positivists. And of these I owe most to Rudolf Carnap. Further, I wish to acknowledge my indebtedness to Gilbert Ryle, my original tutor in philosophy, and to Isaiah Berlin, who have discussed with me every point in the argument of this treatise, and made many valuable suggestions, although they both disagree with much of what I assert.

COMMENT: Abstract is the full text

"Ayer (A.J.) - The Elimination of Metaphysics"

Source: Ayer - Language, Truth and Logic, Chapter 1

  • 45: What is the purpose and method of philosophy? Rejection of the metaphysical thesis that philosophy affords us knowledge of a transcendent reality.
  • 46: Kant also rejected metaphysics in this sense, but whereas he accused metaphysicians of ignoring the limits of the human understanding we accuse them of disobeying the rules which govern the significant use of language.
  • 48: Adoption of verifiability as a criterion for testing the significance of putative statements of fact,
  • 48: Distinction between conclusive and partial verification. No propositions can be conclusively verified.
  • 51: Or conclusively confuted.
  • 52: For a statement of fact to be genuine some possible observations must be relevant to the determination of its truth or falsehood. 53:
    Examples of the kinds of assertions, familiar to philosophers, which are ruled out by our criterion.
  • 56: Metaphysical sentences defined as sentences which express neither tautologies nor empirical hypotheses.
  • 56: Linguistic confusions the prime source of metaphysics.
  • 59: Metaphysics and Poetry.

In-Page Footnotes ("Ayer (A.J.) - The Elimination of Metaphysics")

Footnote 1: These headings were helpfully supplied by Ayer on pp. 37-40 of the 1971 Pelican edition. The numbers refer to the pages in that edition.

"Ayer (A.J.) - The Function of Philosophy"

Source: Ayer - Language, Truth and Logic, Chapter 2

  • 62: Philosophy is not a search for first principles.
  • 62: Barrenness of Descartes' procedure.
  • 65: The function of philosophy is wholly critical. But this does not mean that it can give an a priori justification of our scientific or common-sense assumptions.
  • 66: There is no genuine problem of induction, as ordinarily conceived.
  • 68: Philosophising is an activity of analysis.
  • 69: Most of those who are commonly thought to have been great philosophers were philosophers in our sense, rather than metaphysicians.
  • 70: Locke, Berkeley, Hume as analysts.
  • 71: We adopt Berkeley's phenomenalism without his theism.
  • 72: And take a Humean view of causation2.
  • 75: Philosophy in our sense is wholly independent of metaphysics. We are not committed to any doctrine of atomism.
  • 76: The philosopher as an analyst is not concerned with the physical properties of things, but only with the way in which we speak about them.
  • 77: Linguistic propositions disguised in factual terminology.
  • 78: Philosophy issues in definitions.

In-Page Footnotes ("Ayer (A.J.) - The Function of Philosophy")

Footnote 1: These headings were helpfully supplied by Ayer on pp. 37-40 of the 1971 Pelican edition. The numbers refer to the pages in that edition.

"Ayer (A.J.) - The Nature of Philosophical Analysis"

Source: Ayer - Language, Truth and Logic, Chapter 3

  • 80: Philosophy provides not explicit definitions, such as are given in dictionaries, but definitions in use. Explanation of this distinction.
  • 81: Russell's 'theory of descriptions' as an example of philosophical analysis.
  • 84: Definition of an ambiguous symbol.
  • 85: Definition of a logical construction.
  • 86: Material things are logical constructions out of sense-contents.
  • 86: By defining the notion of a material thing in terms of sense-contents we solve the so-called problem of perception.
  • 87: A solution of this problem outlined as a further example of philosophical analysis.
  • 91: Utility of such analyses.
  • 92: Danger of saying that philosophy is concerned with meaning.
  • 93: The propositions of philosophy are not empirical propositions concerning the way in which people actually use words. They are concerned with the logical consequences of linguistic conventions.
  • 93: Rejection of the view that 'every language has a structure concerning which in the language nothing can be said'.

In-Page Footnotes ("Ayer (A.J.) - The Nature of Philosophical Analysis")

Footnote 1: These headings were helpfully supplied by Ayer on pp. 37-40 of the 1971 Pelican edition. The numbers refer to the pages in that edition.

"Ayer (A.J.) - The A Priori"

Source: Ayer - Language, Truth and Logic, Chapter 4

  • 96: As empiricists, we must deny that any general proposition concerning a matter of fact can be known certainly to be valid.
  • 96: How then are we to deal with the propositions of formal logic and mathematics?.
  • 99: Rejection of Mill's view that these propositions are inductive generalisations.
  • 103: They are necessarily true because they are analytic.
  • 103: Kant's definitions of analytic and synthetic judgements.
  • 105: Emendation of Kant's definitions.
  • 106: Analytic propositions are tautological; they say nothing concerning any matter of fact
  • 106: But they give us new knowledge, inasmuch as they bring to light the implications of our linguistic usages.
  • 108: Logic does not describe 'the laws of thought'.
  • 109: Nor geometry the properties of physical space.
  • 112: Our account of a priori truths undermines Kant's transcendental system.
  • 113: How, if they are tautological, can there be in mathematics and logic the possibility of invention and discovery?

COMMENT: Also in "Benacerraf (Paul) & Putnam (Hilary) - Philosophy of Mathematics - Selected Readings"

In-Page Footnotes ("Ayer (A.J.) - The A Priori")

Footnote 1: These headings were helpfully supplied by Ayer on pp. 37-40 of the 1971 Pelican edition. The numbers refer to the pages in that edition.

"Ayer (A.J.) - Truth and Probability"

Source: Ayer - Language, Truth and Logic, Chapter 5

  • 116: What is truth?
  • 117: Definition of a proposition.
  • 117: The words `true' and 'false' function in the sentence simply as assertion and negation signs.
  • 119: The 'problem, of truth' reduced to the question; How are propositions validated?
  • 120: The criterion of the validity of empirical propositions is not purely formal.
  • 121: No empirical propositions are certain not even those which refer to immediate experience.
  • 125: Observation confirms or discredits not just a single hypothesis but a system of hypotheses.
  • 126: The 'facts of experience' can never compel us to abandon a hypothesis.
  • 128: Danger of mistaking synthetic for analytic propositions.
  • 129: Hypotheses as rules which govern our expectation of future experience.
  • 133: Definition of rationality,
  • 134: Definition of probability in terms of rationality.
  • 134: Propositions referring to the past.

In-Page Footnotes ("Ayer (A.J.) - Truth and Probability")

Footnote 1: These headings were helpfully supplied by Ayer on pp. 37-40 of the 1971 Pelican edition. The numbers refer to the pages in that edition.

"Ayer (A.J.) - Critique of Ethics and Theology"

Source: Ayer - Language, Truth and Logic, Chapter 6

  • 136: How does an empiricist deal with assertions of value?
  • 137: Distinction between various types of ethical enquiry.
  • 138: Utilitarian and subjectivist theories of ethics consistent with empiricism.
  • 139: But unacceptable on other grounds.
  • 140: Distinction between normative and descriptive ethical symbols.
  • 141: Rejection of intuitionism.
  • 142: Assertions of value are not scientific but 'emotive,'
  • 142: They are therefore neither true nor false.
  • 143: They are partly expressions of feeling, partly commands.
  • 145: Distinction between expressions and assertions of feeling.
  • 145: Objection that this view makes it impossible to dispute about questions of value.
  • 146: Actually, we never do dispute about questions of value, but always about questions of fact.
  • 148: Ethics as a branch of knowledge comprehended in the social sciences.
  • 150: The same applies to aesthetics.
  • 151: Impossibility of demonstrating the existence of a transcendent god.
  • 152: Or even of proving it probable.
  • 152: That a transcendent god exists is a metaphysical assertion, and, therefore not literally significant. Saying this does not make us atheists or agnostics in the ordinary sense.
  • 154: The belief that men have immortal souls is also metaphysical.
  • 155: There is no logical ground for conflict between religion and science.
  • 156: Our views supported by the statements of theists themselves.
  • 157: Refutation of the argument from religious experience.

In-Page Footnotes ("Ayer (A.J.) - Critique of Ethics and Theology")

Footnote 1: These headings were helpfully supplied by Ayer on pp. 37-40 of the 1971 Pelican edition. The numbers refer to the pages in that edition.

"Ayer (A.J.) - The Self and the Common World"

Source: Ayer - Language, Truth and Logic, Chapter 7

  • 159: The basis of knowledge.
  • 161: Sense-contents as parts, rather than objects, of sense-experiences.
  • 162: Sense-contents neither mental nor physical.
  • 162: Distinction between the mental and the physical applies only to logical constructions.
  • 164: The existence of epistemological and causal connections between minds and material things open to no a priori objections.
  • 165: Analysis of the self in terms of sense-experiences.
  • 165: A sense-experience cannot belong to the sense-history of more than one self.
  • 166: The substantive ego a fictitious metaphysical entity.
  • 167: Hume's definition of the self.
  • 168: That the empirical self survives the dissolution of the body is a self-contradictory proposition.
  • 168: Does our phenomenalism involve solipsism?
  • 170: Our knowledge of other people.
  • 173: How is mutual understanding possible?

In-Page Footnotes ("Ayer (A.J.) - The Self and the Common World")

Footnote 1: These headings were helpfully supplied by Ayer on pp. 37-40 of the 1971 Pelican edition. The numbers refer to the pages in that edition.

"Ayer (A.J.) - Solutions of Outstanding Philosophical Disputes"

Source: Ayer - Language, Truth and Logic, Chapter 8

  • 176: The nature of philosophy does not warrant the existence of conflicting philosophical 'parties'.
  • 177: The conflict between rationalists and empiricists.
  • 179: Our own logical empiricism to be distinguished from positivism.
  • 180: We reject Hume's psychological, as opposed to his logical, doctrines.
  • 182: Realism and Idealism.
  • 183: To say that a thing exists is not to say that it is actually being perceived.
  • 186: Things as permanent possibilities of sensation.
  • 187: What is perceived is not necessarily mental.
  • 190: What exists need not necessarily be thought of.
  • 190: Nor what is thought of exist.
  • 191: Empirical grounds for supposing that things may exist unperceived.
  • 193: Monism and Pluralism.
  • 193: Monistic fallacy that all a thing's properties are constitutive of is nature.
  • 196: Illustrates the danger of expressing linguistic propositions in factual terminology.
  • 197: Causality2 not a logical relation.
  • 199: Empirical evidence against the monist's view that every event is causally connected with every other.
  • 200: The unity of science.
  • 200: Philosophy as the logic of science.

In-Page Footnotes ("Ayer (A.J.) - Solutions of Outstanding Philosophical Disputes")

Footnote 1: These headings were helpfully supplied by Ayer on pp. 37-40 of the 1971 Pelican edition. The numbers refer to the pages in that edition.

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