36 ideas
| 21959 | Metaphysics is the most general attempt to make sense of things [Moore,AW] |
| Full Idea: Metaphysics is the most general attempt to make sense of things. | |
| From: A.W. Moore (The Evolution of Modern Metaphysics [2012], Intro) | |
| A reaction: This is the first sentence of Moore's book, and a touchstone idea all the way through. It stands up well, because it says enough without committing to too much. I have to agree with it. It implies explanation as the key. I like generality too. |
| 19335 | Reasonings have a natural ordering in God's understanding, but only a temporal order in ours [Leibniz] |
| Full Idea: All reasonings are eminent in God, and they preserve an order among themselves in his understanding as well as in ours; but for him this is just an order and a priority of nature, whereas for us there is a priority of time. | |
| From: Gottfried Leibniz (The Theodicy [1710], p.192), quoted by Franklin Perkins - Leibniz: Guide for the Perplexed 2.III | |
| A reaction: This view is found in Frege, and seems to be the hallmark of rationalist philosophy. There is an apriori assumption that reality has a rational order, so that pure reason is a tool for grasping it. Lewis's 'mosaic' of experiences has no order. |
| 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) |
| 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) |
| 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. |
| 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. |
| 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) |
| 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) |
| 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) |
| 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) |
| 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) |
| 21958 | Appearances are nothing beyond representations, which is transcendental ideality [Moore,AW] |
| Full Idea: Appearances in general are nothing outside our representations, which is just what we mean by transcendental ideality. | |
| From: A.W. Moore (The Evolution of Modern Metaphysics [2012], B535/A507) |
| 19367 | Saying we must will whatever we decide to will leads to an infinite regress [Leibniz] |
| Full Idea: As for volition itself, to say that it is the object of free will is incorrect. We will to act, strictly speaking, and we do not will to will, else we should still say we will to have the will to will, and that would go on to infinity. | |
| From: Gottfried Leibniz (The Theodicy [1710], p.151), quoted by Franklin Perkins - Leibniz: Guide for the Perplexed 4.IV | |
| A reaction: This strikes me as an elementary difficulty which most fans of free will appear to evade. Thoughts just arise in us, and some of them are volitions. We can say there is then a 'gap' (Searle) where we choose, but what happens in the gap? |
| 19351 | Perfections of soul subordinate the body, but imperfections of soul submit to the body [Leibniz] |
| Full Idea: Insofar as the soul has perfection ...God has accommodated the body to the soul, and has arranged beforehand that the body is impelled to execute its orders. Insofar as it is imperfect and confused, God accommodates soul to body, swayed by passions. | |
| From: Gottfried Leibniz (The Theodicy [1710], p.159), quoted by Franklin Perkins - Leibniz: Guide for the Perplexed 3.IV | |
| A reaction: Perkins says this is the nearest Leibniz gets to the idea of interaction between body and soul. Perfection and confusion are on a continuum for Leibniz. With such speculations I always wonder how these things can be known. How perfect is my mind? |
| 19331 | Will is an inclination to pursue something good [Leibniz] |
| Full Idea: One may say that 'will' consists in the inclination to do something in proportion to the good it contains. | |
| From: Gottfried Leibniz (The Theodicy [1710], p.136), quoted by Franklin Perkins - Leibniz: Guide for the Perplexed 2.III | |
| A reaction: This emphasises that the will is faced with options, rather than generating the options. The context is a discussion of the nature of God's will. I think 'will' is a really useful concept, and dislike the Hobbesian rejection of will. |
| 19346 | Most people facing death would happily re-live a similar life, with just a bit of variety [Leibniz] |
| Full Idea: I believe there would be few persons who, being at the point of death, were not content to take up life again, on condition of passing through the same amount of good and evil, provided that it were not the same kind. | |
| From: Gottfried Leibniz (The Theodicy [1710], p.130), quoted by Franklin Perkins - Leibniz: Guide for the Perplexed 2.IV | |
| A reaction: Nice challenge. People who refuse the offer are not necessarily suicidal. He's probably right, but Leibniz doesn't recognise the factor of boredom. Look up the suicide note of the actor George Sanders! One life may be enough. |
| 19340 | Metaphysical evil is imperfection; physical evil is suffering; moral evil is sin [Leibniz] |
| Full Idea: Evil may be taken metaphysically, physically, and morally. Metaphysical evil consists in mere imperfection, physical evil is suffering, and moral evil is sin. | |
| From: Gottfried Leibniz (The Theodicy [1710], p.136), quoted by Franklin Perkins - Leibniz: Guide for the Perplexed 2.IV | |
| A reaction: There seem to be plenty of imperfections in the world which don't look like evil. Or do you only declare it to be an imperfection because it seems to be evil (by some other standard)? Human evil comes from ignorance, so metaphysical explains moral. |
| 19366 | You can't assess moral actions without referring to the qualities of character that produce them [Leibniz] |
| Full Idea: One is more worthy of praise when one owes the action to one's good qualities, and more culpable in proportion as one has been impelled by one's evil qualities; assessing actions without weighing the qualities whence they spring is to talk at random. | |
| From: Gottfried Leibniz (The Theodicy [1710], p.426), quoted by Franklin Perkins - Leibniz: Guide for the Perplexed 4.IV | |
| A reaction: Mill tries to separate judgement of the agent from judgement of the consequences of the action, but I think Leibniz has spotted that just judging outcomes ceases to be a 'moral' judgement. |
| 19326 | God must be intelligible, to select the actual world from the possibilities [Leibniz] |
| Full Idea: The cause of the world must be intelligent: for this existing world being contingent and an infinity of worlds being equally possible, with equal claim to existence, the cause of the world must have regarded all of these worlds to fix on one of them. | |
| From: Gottfried Leibniz (The Theodicy [1710], p.127), quoted by Franklin Perkins - Leibniz: Guide for the Perplexed 2.II | |
| A reaction: A wonderfully Leibnizian way of putting what looks like the design argument. |
| 19327 | The intelligent cause must be unique and all-perfect, to handle all the interconnected possibilities [Leibniz] |
| Full Idea: The intelligent cause ought to be infinite in all ways, and absolutely perfect in power, in wisdom, and in goodness, since it relates to all that which is possible. Also, since all is connected together, there is no ground for admitting more than one. | |
| From: Gottfried Leibniz (The Theodicy [1710], p.128), quoted by Franklin Perkins - Leibniz: Guide for the Perplexed 2.II | |
| A reaction: Notice that Leibniz's possible worlds seem to be all connected together, unlike David Lewis's worlds, which are discrete. Personally I suspect that all perfections will lead to contradiction, though Leibniz strongly argues against it. |
| 19344 | God prefers men to lions, but might not exterminate lions to save one man [Leibniz] |
| Full Idea: It is certain that God sets greater store by a man than a lion; nevertheless it can hardly be said with certainty that God prefers a single man in all respects to the whole of lion-kind. | |
| From: Gottfried Leibniz (The Theodicy [1710], p.189), quoted by Franklin Perkins - Leibniz: Guide for the Perplexed 2.IV | |
| A reaction: Lovely problems arise when you guess at God's values! We have the same problem. Would you kill a poacher who was wiping out the last remaining lions? How many lions would you kill to save a human? |
| 19330 | If justice is arbitrary, or fixed but not observed, or not human justice, this undermines God [Leibniz] |
| Full Idea: The three dogmas (1) that the nature of justice is arbitrary, (2) it is fixed, but not certain God will observe it, or (3) the justice we know is not that which God observes, destroy our confidence in the love of God. | |
| From: Gottfried Leibniz (The Theodicy [1710], p.237), quoted by Franklin Perkins - Leibniz: Guide for the Perplexed 2.III | |
| A reaction: Leibniz proceeds to carefully refute these three responses to the dilemma about how justice relates to God. |
| 19325 | God is the first reason of things; our experiences are contingent, and contain no necessity [Leibniz] |
| Full Idea: God is the first reason of things: all that we see and experience is contingent and nothing in them renders their existence necessary. | |
| From: Gottfried Leibniz (The Theodicy [1710], p.127), quoted by Franklin Perkins - Leibniz: Guide for the Perplexed 2.II | |
| A reaction: Perkins presents this as the first step in one of Leibniz's arguments for God. They all seem to be variants of the ontological argument. [His 'Theodicy' is the Huggard translation, 1985] This resembles Aquinas's Third Way. |
| 19329 | The laws of physics are wonderful evidence of an intelligent and free being [Leibniz] |
| Full Idea: These admirable laws [of physics] are wonderful evidence of an intelligent and free being, as opposed to the system of absolute and brute necessity, advocated by Strato and Spinoza. | |
| From: Gottfried Leibniz (The Theodicy [1710], p.332), quoted by Franklin Perkins - Leibniz: Guide for the Perplexed 2.II | |
| A reaction: Note the swipe at Spinoza. Leibniz defends the absolute necessities residing in God, but is too polite to call those 'brute', though personally I can't see the difference. But he says the laws arise from 'perfection and order', not from God's necessity. |
| 19437 | Prayers are useful, because God foresaw them in his great plan [Leibniz] |
| Full Idea: Not only cares and labours but also prayers are useful; God having had these prayers in view before he regulated things. | |
| From: Gottfried Leibniz (The Theodicy [1710], Abridge III) | |
| A reaction: Hm. I'm struggling with this one. So I can't skip prayers today, because God has foreseen them and included them in his great plan? Hard to motivate yourself, like starting a game of chess after you've already been declared the winner. |
| 19337 | How can an all-good, wise and powerful being allow evil, sin and apparent injustice? [Leibniz] |
| Full Idea: There is this question of natural theology, how a sole Principle, all-good, all-wise and all-powerful, has been able to admit evil, and especially to permit sin, and how it could resolve to make the wicked often happy and the good unhappy? | |
| From: Gottfried Leibniz (The Theodicy [1710], p.098), quoted by Franklin Perkins - Leibniz: Guide for the Perplexed 2.IV | |
| A reaction: His answer is, roughly, that there is an unavoidable trade-off, which humans cannot fully understand. Personally I would say that if there is a God, the evidence for his benevolence towards humanity is not encouraging. |
| 19345 | Being confident of God's goodness, we disregard the apparent local evils in the visible world [Leibniz] |
| Full Idea: Being made confident by demonstrations of the goodness and the justice of God, we disregard the appearances of harshness and justice which we see in this small portion of his Kingdom that is exposed to our gaze. | |
| From: Gottfried Leibniz (The Theodicy [1710], p.120), quoted by Franklin Perkins - Leibniz: Guide for the Perplexed 2.IV | |
| A reaction: Hm. If this locality is full of evils, and the rest of it is much better, how come we are stuck in this miserable corner of things? God is obliged to compromise, but did he select us to get the worst of it? |