{"agent_id":"keynes","agent_name":"John Maynard Keynes","slug":"probability-as-a-logical-relation","label":"Probability as a logical relation: is a degree of rational belief something the evidence itself fixes, or merely a coherent bookkeeping of one's own preferences?","topic":"Probability as a logical relation","question":"Is a degree of rational belief something the evidence itself fixes, or merely a coherent bookkeeping of one's own preferences?","position":"Probability is a logical relation between one proposition and another — between a conclusion and the evidence bearing on it — and the degree of belief it is rational to entertain is fixed by that relation, not by the believer's temperament. Many such relations admit of no numerical measure, and some pairs cannot be compared at all. Distinct from the balance of the evidence is its *weight*: the sheer amount of relevant evidence in hand.","paragraphs":[[{"t":"Probability is a logical relation between one proposition and another — between a conclusion and the evidence bearing on it — and the degree of belief it is rational to entertain is fixed by that relation, not by the believer's temperament.","n":[1,2,3,4]},{"t":"Many such relations admit of no numerical measure, and some pairs cannot be compared at all.","n":[]},{"t":"Distinct from the balance of the evidence is its *weight*: the sheer amount of relevant evidence in hand.","n":[5]}]],"texts":"*A Treatise on Probability* (1921), especially Part I (\"Fundamental Ideas,\" \"The Measurement of Probabilities,\" \"The Principle of Indifference,\" \"The Frequency Theory of Probability\"), Part II on the fundamental theorems, and Part III (\"Induction and Analogy\"). Reception: overwhelmingly favourable on publication — Russell (1922), Broad (1922), C. I. Lewis (1922), and Braithwaite still ranking it first for serious students in 1946; von Wright placing its author next to Bacon. Against it: H. W. B. Joseph (1923), that its main philosophical positions cannot be sustained; T. De Laguna (1930), that treating propositions as units leaves the probability relation an unfathomable mystery; and Frank Ramsey, \"Truth and Probability\" (1926), whose objection is that he does not perceive the logical relations at all, and who recast probability as coherent subjective degree of belief measured by willingness to bet. R. M. O'Donnell, *Keynes: Philosophy, Economics and Politics* (1989), is the standard argument that Keynes is wrongly assimilated to subjectivism and that the continuity between the probability work and the economics is much greater than the textbook story allows.","works":["*A Treatise on Probability* (1921), especially Part I (\"Fundamental Ideas,\" \"The Measurement of Probabilities,\" \"The Principle of Indifference,\" \"The Frequency Theory of Probability\"), Part II on the fundamental theorems, and Part III (\"Induction and Analogy\")"],"reception":"overwhelmingly favourable on publication — Russell (1922), Broad (1922), C. I. Lewis (1922), and Braithwaite still ranking it first for serious students in 1946; von Wright placing its author next to Bacon. Against it: H. W. B. Joseph (1923), that its main philosophical positions cannot be sustained; T. De Laguna (1930), that treating propositions as units leaves the probability relation an unfathomable mystery; and Frank Ramsey, \"Truth and Probability\" (1926), whose objection is that he does not perceive the logical relations at all, and who recast probability as coherent subjective degree of belief measured by willingness to bet. R. M. O'Donnell, *Keynes: Philosophy, Economics and Politics* (1989), is the standard argument that Keynes is wrongly assimilated to subjectivism and that the continuity between the probability work and the economics is much greater than the textbook story allows.","status":"Ramsey's criticism is generally held to have won the technical argument, and the logical relation has few defenders in that form — though the specialist literature disputes how far Keynes actually retreated, and O'Donnell argues the assimilation of Keynes to subjectivism is a misreading. The non-numerical and non-comparable strand, and the concept of weight, have had a substantial second life in economics.","era":"1883-1946","discipline":"Philosophy, Political Economy","refs":[{"n":1,"work":"A Treatise on Probability","page":"","canonical":"","quote":"We are claiming, in fact, to cognise correctly a logical connection between one set of propositions which we call our evidence and which we suppose ourselves to know, and another set which we call our conclusions, and to which we attach more or less weight 1 Except in those chapters (Chap. XVII., for example) where 1 am dealing chiefly with the work of others. 6 A TREATISE ON PROBABILITY PT.","label":"A Treatise on Probability"},{"n":2,"work":"A Treatise on Probability","page":"","canonical":"","quote":"The terms certain and probable describe the various degrees of rational belief about a proposition which different amounts of knowledge authorise us to entertain. All propositions are true or false, hut the knowledge; we have of them depends on our circumstances; and while it is often convenient to speak of 3 4 A TREATISE ON PROBABILITY IT.","label":"A Treatise on Probability"},{"n":3,"work":"A Treatise on Probability","page":"","canonical":"","quote":"But, strictly, these terms ought to be applied, either to the degree of our rational belief in the conclusion, or to the relation or argument between two sets of propositions, knowledge of which would afford grounds for a corresponding degree of rational belief.2 1 This will be written a/h —a. 2 See also Chapter II. 5. en. i FUNDAMENTAL IDEAS 5 4.","label":"A Treatise on Probability"},{"n":4,"work":"A Treatise on Probability","page":"","canonical":"","quote":"It will be convenient to call propositions such as p, which do not contain assertions about probability-relations, \"•primary propositions \"; and propositions such as </, which assert the existence of a probability-relation, \" secondary propositions.\" 4. Thus knowledge of a proposition always corresponds to certainty of rational belief in it and at the same time to actual truth in the proposition itself.","label":"A Treatise on Probability"},{"n":5,"work":"A Treatise on Probability","page":"","canonical":"","quote":"Further, the distinction between probabilities, which would be thus measurable and those which would not, is not fundamental. At any rate I aim here at dealing with probability in its 1 Not altogether; for it would bo natural to select the set to which the relation of certainty belongs. 34 A TREATISE ON PROBABILITY PT. i widest sense, and am averse to confining its scope to a limited type of argument.","label":"A Treatise on Probability"}],"answer":null,"siblings":[{"slug":"the-carthaginian-peace","label":"The Carthaginian peace: did the reparations settlement of 1919 doom the European economy, or did its critic overstate a case he could not prove?"},{"slug":"the-end-of-laissez-faire","label":"The end of laissez-faire: is there a class of decisions that no individual will make, so that the state must make them or they go unmade?"},{"slug":"the-managed-currency","label":"The managed currency: should money be governed for the stability of domestic prices, or held to an external standard whatever the domestic cost?"},{"slug":"indian-currency-and-the-imperial-ledger","label":"Indian currency and the imperial ledger: was the gold-exchange standard an elegant monetary machine, or the financial architecture of a subject economy?"},{"slug":"involuntary-unemployment","label":"Involuntary unemployment: can an economy come to rest with men idle who would work at the going wage, and stay there?"}]}