27 ideas
| 7460 | The great moments are the death of Aristotle, Machiavelli, and Romanticism [Berlin, by Watson] |
| Full Idea: Berlin says there were three great turning points: after the death of Aristotle (when Greek schools focused on the inner life of individuals, instead of as social beings), Machiavelli's division of political and individual virtues, and Romanticism. | |
| From: report of Isaiah Berlin (The Sense of Reality [1996], p.168-9) by Peter Watson - Ideas Intro | |
| A reaction: I have the impression that Machiavelli introduced a new hard-boiled ethics, which dominated the sixteenth century, but in the seventeenth and eighteenth century they fought back, and Machiavellianism turned out to be just a phase. |
| 7662 | Romanticism is the greatest change in the consciousness of the West [Berlin] |
| Full Idea: Romanticism seems to me the greatest single shift in the consciousness of the West that has occurred. | |
| From: Isaiah Berlin (The Roots of Romanticism [1965], Ch.1) | |
| A reaction: Far be it from me to challenge Berlin on such things, but I think that the scientific revolution of the seventeenth century (though acting more slowly and less dramatically than romanticism) may well be more significant in the long run. Ideas filter down. |
| 10888 | Sets can be defined by 'enumeration', or by 'abstraction' (based on a property) [Zalabardo] |
| Full Idea: We can define a set by 'enumeration' (by listing the items, within curly brackets), or by 'abstraction' (by specifying the elements as instances of a property), pretending that they form a determinate totality. The latter is written {x | x is P}. | |
| From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §1.3) |
| 10889 | The 'Cartesian Product' of two sets relates them by pairing every element with every element [Zalabardo] |
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Full Idea:
The 'Cartesian Product' of two sets, written A x B, is the relation which pairs every element of A with every element of B. So A x B = { |
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| From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §1.6) |
| 10890 | A 'partial ordering' is reflexive, antisymmetric and transitive [Zalabardo] |
| Full Idea: A binary relation in a set is a 'partial ordering' just in case it is reflexive, antisymmetric and transitive. | |
| From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §1.6) |
| 10886 | Determinacy: an object is either in a set, or it isn't [Zalabardo] |
| Full Idea: Principle of Determinacy: For every object a and every set S, either a is an element of S or a is not an element of S. | |
| From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §1.2) |
| 10887 | Specification: Determinate totals of objects always make a set [Zalabardo] |
| Full Idea: Principle of Specification: Whenever we can specify a determinate totality of objects, we shall say that there is a set whose elements are precisely the objects that we have specified. | |
| From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §1.3) | |
| A reaction: Compare the Axiom of Specification. Zalabardo says we may wish to consider sets of which we cannot specify the members. |
| 10897 | A first-order 'sentence' is a formula with no free variables [Zalabardo] |
| Full Idea: A formula of a first-order language is a 'sentence' just in case it has no free variables. | |
| From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §3.2) |
| 10893 | Γ |= φ for sentences if φ is true when all of Γ is true [Zalabardo] |
| Full Idea: A propositional logic sentence is a 'logical consequence' of a set of sentences (written Γ |= φ) if for every admissible truth-assignment all the sentences in the set Γ are true, then φ is true. | |
| From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §2.4) | |
| A reaction: The definition is similar for predicate logic. |
| 10899 | Γ |= φ if φ is true when all of Γ is true, for all structures and interpretations [Zalabardo] |
| Full Idea: A formula is the 'logical consequence' of a set of formulas (Γ |= φ) if for every structure in the language and every variable interpretation of the structure, if all the formulas within the set are true and the formula itself is true. | |
| From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §3.5) |
| 10896 | Propositional logic just needs ¬, and one of ∧, ∨ and → [Zalabardo] |
| Full Idea: In propositional logic, any set containing ¬ and at least one of ∧, ∨ and → is expressively complete. | |
| From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §2.8) |
| 10898 | The semantics shows how truth values depend on instantiations of properties and relations [Zalabardo] |
| Full Idea: The semantic pattern of a first-order language is the ways in which truth values depend on which individuals instantiate the properties and relations which figure in them. ..So we pair a truth value with each combination of individuals, sets etc. | |
| From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §3.3) | |
| A reaction: So truth reduces to a combination of 'instantiations', which is rather like 'satisfaction'. |
| 10902 | We can do semantics by looking at given propositions, or by building new ones [Zalabardo] |
| Full Idea: We can look at semantics from the point of view of how truth values are determined by instantiations of properties and relations, or by asking how we can build, using the resources of the language, a proposition corresponding to a given semantic pattern. | |
| From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §3.6) | |
| A reaction: The second version of semantics is model theory. |
| 10892 | We make a truth assignment to T and F, which may be true and false, but merely differ from one another [Zalabardo] |
| Full Idea: A truth assignment is a function from propositions to the set {T,F}. We will think of T and F as the truth values true and false, but for our purposes all we need to assume about the identity of these objects is that they are different from each other. | |
| From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §2.4) | |
| A reaction: Note that T and F are 'objects'. This remark is important in understanding modern logical semantics. T and F can be equated to 1 and 0 in the language of a computer. They just mean as much as you want them to mean. |
| 10895 | 'Logically true' (|= φ) is true for every truth-assignment [Zalabardo] |
| Full Idea: A propositional logic sentence is 'logically true', written |= φ, if it is true for every admissible truth-assignment. | |
| From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §2.4) |
| 10900 | Logically true sentences are true in all structures [Zalabardo] |
| Full Idea: In first-order languages, logically true sentences are true in all structures. | |
| From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §3.5) |
| 10894 | A sentence-set is 'satisfiable' if at least one truth-assignment makes them all true [Zalabardo] |
| Full Idea: A propositional logic set of sentences Γ is 'satisfiable' if there is at least one admissible truth-assignment that makes all of its sentences true. | |
| From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §2.4) |
| 10901 | Some formulas are 'satisfiable' if there is a structure and interpretation that makes them true [Zalabardo] |
| Full Idea: A set of formulas of a first-order language is 'satisfiable' if there is a structure and a variable interpretation in that structure such that all the formulas of the set are true. | |
| From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §3.5) |
| 10903 | A structure models a sentence if it is true in the model, and a set of sentences if they are all true in the model [Zalabardo] |
| Full Idea: A structure is a model of a sentence if the sentence is true in the model; a structure is a model of a set of sentences if they are all true in the structure. | |
| From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §3.6) |
| 10891 | If a set is defined by induction, then proof by induction can be applied to it [Zalabardo] |
| Full Idea: Defining a set by induction enables us to use the method of proof by induction to establish that all the elements of the set have a certain property. | |
| From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §2.3) |
| 7665 | Most Enlightenment thinkers believed that virtue consists ultimately in knowledge [Berlin] |
| Full Idea: What is common to most of the main thinker of the Enlightenment is the view that virtue consists ultimately in knowledge. | |
| From: Isaiah Berlin (The Roots of Romanticism [1965], Ch.2) | |
| A reaction: I have always found this view (which seems to originate with Socrates) rather sympathetic. What is so frustrating about cheerful optimists who smoke cigarettes is not the weakness of will or strong desires, but their apparent failure of understanding. |
| 7676 | If we are essentially free wills, authenticity and sincerity are the highest virtues [Berlin] |
| Full Idea: Since (for romantics) we are wills, and we must be free, in the Kantian sense, controllable motives count more than consequences, and the greatest virtue of all is what existentialists call 'authenticity' and what romantics called 'sincerity'. | |
| From: Isaiah Berlin (The Roots of Romanticism [1965], Ch.6) | |
| A reaction: The case of the sincere or authentic Nazi shows the problems with this. However, I agree that sincerity is a key virtue, perhaps the crucial preliminary to all the other virtues. It is hard to imagine a flow of other virtues from an insincere person. |
| 7664 | The Greeks have no notion of obligation or duty [Berlin] |
| Full Idea: There is an absence among the Greeks of a notion of obligation, and hence of duty, which is difficult to grasp for people who read the Greeks through spectacles partly affected by the jews. | |
| From: Isaiah Berlin (The Roots of Romanticism [1965], Ch.1) | |
| A reaction: This doesn't quite fit early section of 'Republic', in which morality is a mutual agreement not to do harm. Presumably the Greek word 'deon' refers to what needs to be done, rather than to anyone's obligation to do it(?). Contracts need duty? Cf. 4133 |
| 7677 | Central to existentialism is the romantic idea that there is nothing to lean on [Berlin] |
| Full Idea: The central sermon of existentialism is essentially a romantic one, namely, that there is in the world nothing to lean on. | |
| From: Isaiah Berlin (The Roots of Romanticism [1965], Ch.6) | |
| A reaction: He tracks this back to Kant's view that our knowledge of the world arises out of our own minds. So what is there to lean on? Rational consistency? Natural human excellence? God? Pleasure? Anonymous duty? I like the second one. |
| 20544 | Berlin distinguishes 'negative' and 'positive' liberty, and rejects the latter [Berlin, by Swift] |
| Full Idea: Isaiah Berlin draws a famous distinction between 'negative' and 'positive' concepts of liberty, and argues that the latter should be seen as a wrong turning (because totalitarian regimes have invoked it). | |
| From: report of Isaiah Berlin (Two Concepts of Liberty [1958]) by Adam Swift - Political Philosophy (3rd ed) 2 'Intro' | |
| A reaction: Swift argues against him, saying that positive liberty is not a single concept (it's three), and has aspects that should be defended. I think I'm with Swift on that. Is religious freedom a freedom 'from' something, or a freedom 'to do' something? |
| 6005 | Animals are dangerous and nourishing, and can't form contracts of justice [Hermarchus, by Sedley] |
| Full Idea: Hermarchus said that animal killing is justified by considerations of human safety and nourishment and by animals' inability to form contractual relations of justice with us. | |
| From: report of Hermarchus (fragments/reports [c.270 BCE]) by David A. Sedley - Hermarchus | |
| A reaction: Could the last argument be used to justify torturing animals? Or could we eat a human who was too brain-damaged to form contracts? |
| 7663 | Judaism and Christianity views are based on paternal, family and tribal relations [Berlin] |
| Full Idea: The notion from which both Judaism and Christianity to a large degree sprang is the notion of family life, the relations of father and son, perhaps the relations of members of a tribe to one another. | |
| From: Isaiah Berlin (The Roots of Romanticism [1965], Ch.1) | |
| A reaction: He compares this with Plato's mathematical view of reality. Key stories would be Abraham and Isaac, and Jesus being the 'son' of God, which both touch the killing of the child. Berlin means that the universe is explained this way. |