76 ideas
| 17240 | Definitions are the first step in philosophy [Hobbes] |
| Full Idea: In beginning philosophy, the first beginning is from definitions. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 1.6.15) | |
| A reaction: Note that he doesn't say that definitions are the aim of philosophy, as some analysts might think. |
| 17237 | Definitions of things that are caused must express their manner of generation [Hobbes] |
| Full Idea: Definitions of things which may be understood to have some cause, must consist of such names as express the cause or manner of their generation, as when we define a circle to be a figure made by the circumduction of a straight line in a plane etc. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 1.6.13) | |
| A reaction: His account of the circle is based on its mode of construction, which is the preferred account of Euclid, rather than a statement of its pure nature. |
| 17239 | Definition is resolution of names into successive genera, and finally the difference [Hobbes] |
| Full Idea: The definition is nothing but a resolution of the name into its most universal parts; ...definitions of this kind always consist of genus and difference; the former names being all, till the last, general; and the last of all, difference. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 1.6.14) | |
| A reaction: This is basically the scholastic Aristotelian view of definition. Note that Hobbes explicitly denies that the last step of the definition is general in character. |
| 17241 | A defined name should not appear in the definition [Hobbes] |
| Full Idea: A defined name ought not to be repeated in the definition. ...No total can be part of itself. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 1.6.15) |
| 17242 | 'Petitio principii' is reusing the idea to be defined, in disguised words [Hobbes] |
| Full Idea: 'Petitio principii' is when the conclusion to be proved is disguised in other words, and put for the definition or principle from whence it is to be demonstrated. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 1.6.18) |
| 9724 | Until the 1960s the only semantics was truth-tables [Enderton] |
| Full Idea: Until the 1960s standard truth-table semantics were the only ones that there were. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.10.1) | |
| A reaction: The 1960s presumably marked the advent of possible worlds. |
| 9703 | 'dom R' indicates the 'domain' of objects having a relation [Enderton] |
| Full Idea: 'dom R' indicates the 'domain' of a relation, that is, the set of all objects that are members of ordered pairs and that have that relation. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9705 | 'fld R' indicates the 'field' of all objects in the relation [Enderton] |
| Full Idea: 'fld R' indicates the 'field' of a relation, that is, the set of all objects that are members of ordered pairs on either side of the relation. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9704 | 'ran R' indicates the 'range' of objects being related to [Enderton] |
| Full Idea: 'ran R' indicates the 'range' of a relation, that is, the set of all objects that are members of ordered pairs and that are related to by the first objects. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9710 | We write F:A→B to indicate that A maps into B (the output of F on A is in B) [Enderton] |
| Full Idea: We write F : A → B to indicate that A maps into B, that is, the domain of relating things is set A, and the things related to are all in B. If we add that F = B, then A maps 'onto' B. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9707 | 'F(x)' is the unique value which F assumes for a value of x [Enderton] |
|
Full Idea:
F(x) is a 'function', which indicates the unique value which y takes in |
|
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9712 | A relation is 'symmetric' on a set if every ordered pair has the relation in both directions [Enderton] |
| Full Idea: A relation is 'symmetric' on a set if every ordered pair in the set has the relation in both directions. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9713 | A relation is 'transitive' if it can be carried over from two ordered pairs to a third [Enderton] |
| Full Idea: A relation is 'transitive' on a set if the relation can be carried over from two ordered pairs to a third. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9699 | The 'powerset' of a set is all the subsets of a given set [Enderton] |
| Full Idea: The 'powerset' of a set is all the subsets of a given set. Thus: PA = {x : x ⊆ A}. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9700 | Two sets are 'disjoint' iff their intersection is empty [Enderton] |
| Full Idea: Two sets are 'disjoint' iff their intersection is empty (i.e. they have no members in common). | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9702 | A 'domain' of a relation is the set of members of ordered pairs in the relation [Enderton] |
| Full Idea: The 'domain' of a relation is the set of all objects that are members of ordered pairs that are members of the relation. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9701 | A 'relation' is a set of ordered pairs [Enderton] |
| Full Idea: A 'relation' is a set of ordered pairs. The ordering relation on the numbers 0-3 is captured by - in fact it is - the set of ordered pairs {<0,1>,<0,2>,<0,3>,<1,2>,<1,3>,<2,3>}. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) | |
| A reaction: This can't quite be a definition of order among numbers, since it relies on the notion of a 'ordered' pair. |
| 9706 | A 'function' is a relation in which each object is related to just one other object [Enderton] |
| Full Idea: A 'function' is a relation which is single-valued. That is, for each object, there is only one object in the function set to which that object is related. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9708 | A function 'maps A into B' if the relating things are set A, and the things related to are all in B [Enderton] |
| Full Idea: A function 'maps A into B' if the domain of relating things is set A, and the things related to are all in B. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9709 | A function 'maps A onto B' if the relating things are set A, and the things related to are set B [Enderton] |
| Full Idea: A function 'maps A onto B' if the domain of relating things is set A, and the things related to are set B. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9711 | A relation is 'reflexive' on a set if every member bears the relation to itself [Enderton] |
| Full Idea: A relation is 'reflexive' on a set if every member of the set bears the relation to itself. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9714 | A relation satisfies 'trichotomy' if all pairs are either relations, or contain identical objects [Enderton] |
| Full Idea: A relation satisfies 'trichotomy' on a set if every ordered pair is related (in either direction), or the objects are identical. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9717 | A set is 'dominated' by another if a one-to-one function maps the first set into a subset of the second [Enderton] |
| Full Idea: A set is 'dominated' by another if a one-to-one function maps the first set into a subset of the second. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9715 | An 'equivalence relation' is a reflexive, symmetric and transitive binary relation [Enderton] |
| Full Idea: An 'equivalence relation' is a binary relation which is reflexive, and symmetric, and transitive. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9716 | We 'partition' a set into distinct subsets, according to each relation on its objects [Enderton] |
| Full Idea: Equivalence classes will 'partition' a set. That is, it will divide it into distinct subsets, according to each relation on the set. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 17245 | A part of a part is a part of a whole [Hobbes] |
| Full Idea: A part of a part is a part of a whole. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.07.09) |
| 9722 | Inference not from content, but from the fact that it was said, is 'conversational implicature' [Enderton] |
| Full Idea: The process is dubbed 'conversational implicature' when the inference is not from the content of what has been said, but from the fact that it has been said. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.7.3) |
| 9718 | Validity is either semantic (what preserves truth), or proof-theoretic (following procedures) [Enderton] |
| Full Idea: The point of logic is to give an account of the notion of validity,..in two standard ways: the semantic way says that a valid inference preserves truth (symbol |=), and the proof-theoretic way is defined in terms of purely formal procedures (symbol |-). | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.1.3..) | |
| A reaction: This division can be mirrored in mathematics, where it is either to do with counting or theorising about things in the physical world, or following sets of rules from axioms. Language can discuss reality, or play word-games. |
| 9721 | A logical truth or tautology is a logical consequence of the empty set [Enderton] |
| Full Idea: A is a logical truth (tautology) (|= A) iff it is a semantic consequence of the empty set of premises (φ |= A), that is, every interpretation makes A true. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.3.4) | |
| A reaction: So the final column of every line of the truth table will be T. |
| 9994 | A truth assignment to the components of a wff 'satisfy' it if the wff is then True [Enderton] |
| Full Idea: A truth assignment 'satisfies' a formula, or set of formulae, if it evaluates as True when all of its components have been assigned truth values. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.2) | |
| A reaction: [very roughly what Enderton says!] The concept becomes most significant when a large set of wff's is pronounced 'satisfied' after a truth assignment leads to them all being true. |
| 9719 | A proof theory is 'sound' if its valid inferences entail semantic validity [Enderton] |
| Full Idea: If every proof-theoretically valid inference is semantically valid (so that |- entails |=), the proof theory is said to be 'sound'. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.1.7) |
| 9720 | A proof theory is 'complete' if semantically valid inferences entail proof-theoretic validity [Enderton] |
| Full Idea: If every semantically valid inference is proof-theoretically valid (so that |= entails |-), the proof-theory is said to be 'complete'. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.1.7) |
| 9995 | Proof in finite subsets is sufficient for proof in an infinite set [Enderton] |
| Full Idea: If a wff is tautologically implied by a set of wff's, it is implied by a finite subset of them; and if every finite subset is satisfiable, then so is the whole set of wff's. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 2.5) | |
| A reaction: [Enderton's account is more symbolic] He adds that this also applies to models. It is a 'theorem' because it can be proved. It is a major theorem in logic, because it brings the infinite under control, and who doesn't want that? |
| 9996 | Expressions are 'decidable' if inclusion in them (or not) can be proved [Enderton] |
| Full Idea: A set of expressions is 'decidable' iff there exists an effective procedure (qv) that, given some expression, will decide whether or not the expression is included in the set (i.e. doesn't contradict it). | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.7) | |
| A reaction: This is obviously a highly desirable feature for a really reliable system of expressions to possess. All finite sets are decidable, but some infinite sets are not. |
| 9997 | For a reasonable language, the set of valid wff's can always be enumerated [Enderton] |
| Full Idea: The Enumerability Theorem says that for a reasonable language, the set of valid wff's can be effectively enumerated. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 2.5) | |
| A reaction: There are criteria for what makes a 'reasonable' language (probably specified to ensure enumerability!). Predicates and functions must be decidable, and the language must be finite. |
| 17258 | If we just say one, one, one, one, we don't know where we have got to [Hobbes] |
| Full Idea: By saying one, one, one, one, and so forward, we know not what number we are at beyond two or three. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.12.05) | |
| A reaction: This makes ordinals sound like meta-numbers. |
| 17253 | Change is nothing but movement [Hobbes] |
| Full Idea: All mutation consists in motion only | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.09.06) | |
| A reaction: Another little gem of simplicity from Hobbes, and one with which I am inclined to agree. The value of a variable can 'change', but that may be metaphorical. |
| 16670 | Accidents are just modes of thinking about bodies [Hobbes] |
| Full Idea: An accident is a mode of conceiving a body. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.08.02) | |
| A reaction: In contrast to the other thinkers who followed Suárez on modes in the early 17th century, Hobbes thinks they are just ways of 'conceiving' bodies, rather than actual features of them. |
| 16621 | Accidents are not parts of bodies (like blood in a cloth); they have accidents as things have a size [Hobbes] |
| Full Idea: An accident's being in a body is not to be taken as something contained in that body - as if redness were in blood like blood in a bloody cloth, as part of the whole, for then accident would be a body. It is like body having size or rest or movement. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.08.03) | |
| A reaction: [compressed] Hobbes is fishing for something like the Quinean view of properties, but no one seems to be able to articulate this sceptical view very well. Pasnau says he means to talk of 'the mode of conceiving a body' (De C 8.2). |
| 16734 | The complete power of an event is just the aggregate of the qualities that produced it [Hobbes] |
| Full Idea: The power of agent and patient taken together, which may be called the complete power, is the same as the complete cause, for each consists in the aggregation together of all the accidents that are required to produce an effect in both agent and patient. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.10.01) | |
| A reaction: They treat powers as macro phenomena, and don't seem to have a sense of the basic powers that build up the big picture. |
| 17247 | The only generalities or universals are names or signs [Hobbes] |
| Full Idea: Nothing is general or universal besides names or signs. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.08.05) | |
| A reaction: This is the perfect motto for nominalists, among which I am inclined to include myself. Hobbes had a fabulous gift for economy of phrasing. This website is dedicated to that ideal. Reality does not contain generalities (obviously!!). |
| 14960 | Bodies are independent of thought, and coincide with part of space [Hobbes] |
| Full Idea: A body is that, which having no dependence on our thought, is coincident or coextended with some part of space. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.08.01) | |
| A reaction: This rather Cartesian view doesn't seem to offer any distinction between empty space and space containing an 'object'. Presumably it is the ancestor of the Quinean account just in terms of space-time points. Don't like it. |
| 17250 | If you separate the two places of one thing, you will also separate the thing [Hobbes] |
| Full Idea: One body cannot be in two places at the same time, ...for the place that a body fills being divided into two, the placed body will also be divided into two; the place and the body that fills that place are divided both together. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.08.08) | |
| A reaction: If every time you manipulated one body it affected both of them, you might say that one body was in two places, rather like a mirror image. |
| 17249 | If you separated two things in the same place, you would also separate the places [Hobbes] |
| Full Idea: Two bodies cannot be together in the same place, ..because when a body that fills its whole place is divided into two, the place itself is divided into two also, so that there will be two places. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.08.08) | |
| A reaction: The wonderful things about philosophy is that you are faced with obvious truths of the world, and cannot begin to think why they are true - and then up steps a philosopher and offers you a reason. |
| 17248 | If a whole body is moved, its parts must move with it [Hobbes] |
| Full Idea: How can any whole body be moved, unless all its parts be moved together with it? | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.08.05) | |
| A reaction: This might be a distinguishing mark for a whole physical body. I think it is probably the main mark for ordinary folk. I've never found this idea in Aristotle. |
| 16078 | Clay is intrinsically and atomically the same as statue (and that lacks 'modal properties') [Rudder Baker] |
| Full Idea: Arguments for statue being the clay are: that the clay is intrinsically like the statue, that the clay has the same atoms as the statue', that objects don't have modal properties such as being necessarily F, and the reference of 'property' changes. | |
| From: Lynne Rudder Baker (Why Constitution is not Identity [1997], II) | |
| A reaction: [my summary of the arguments she identifies - see text for details] Rudder Baker attempts to refute all four of these arguments, in defence of constitution as different from identity. |
| 16077 | The clay is not a statue - it borrows that property from the statue it constitutes [Rudder Baker] |
| Full Idea: I argue that a lump of clay borrows the property of being a statue from the statue. The lump is a statue because, and only because, there is something that the lump constitutes that is a statue. | |
| From: Lynne Rudder Baker (Why Constitution is not Identity [1997], n9) | |
| A reaction: It is skating on very thin metaphysical ice to introduce the concept of 'borrowing' a property. I've spent the last ten minutes trying to 'borrow' some properties, but without luck. |
| 16080 | Is it possible for two things that are identical to become two separate things? [Rudder Baker] |
| Full Idea: A strong intuition shared by many philosophers is that some things that are in fact identical might not have been identical. | |
| From: Lynne Rudder Baker (Why Constitution is not Identity [1997], IV) | |
| A reaction: This flies in the face of the Kripkean view that if Hesperus=Phosphorus then the identity is necessary. I don't think I have an intuition that some given thing might have been two things - indeed the thought seems totally weird. Amoeba? Statue/clay? |
| 16076 | Constitution is not identity, as consideration of essential predicates shows [Rudder Baker] |
| Full Idea: I want to resuscitate an essentialist argument against the view that constitution is identity, of the form 'x is essentially F, y is not essentially F, so x is not y'. | |
| From: Lynne Rudder Baker (Why Constitution is not Identity [1997], Intro) | |
| A reaction: The point is that x might be essentially F and y only accidentally F. Thus a statue is essentially so, but a lump if clay is not essentially a statue. Another case where 'necessary' would do instead of 'essentially'. |
| 16081 | The constitution view gives a unified account of the relation of persons/bodies, statues/bronze etc [Rudder Baker] |
| Full Idea: Constitution-without-identity is superior to constitution-as-identity in that it provides a unified view of the relation between persons and bodies, statues and pieces of bronze, and so on. | |
| From: Lynne Rudder Baker (Why Constitution is not Identity [1997], IV) | |
| A reaction: I have a problem with the intrinsic dualism of this whole picture. Clay needs shape, statues need matter - there aren't two 'things' here which have a 'relation'. |
| 16082 | Statues essentially have relational properties lacked by lumps [Rudder Baker] |
| Full Idea: The statue has relational properties which the lump of clay does not have essentially. | |
| From: Lynne Rudder Baker (Why Constitution is not Identity [1997], V) | |
| A reaction: She has in mind relations to the community of artistic life. I don't think this is convincing. Is something only a statue if it is validated by an artistic community? That sounds like relative identity, which she doesn't like. |
| 16790 | A body is always the same, whether the parts are together or dispersed [Hobbes] |
| Full Idea: A body is always the same, whether the parts of it be put together or dispersed; or whether it be congealed or dissolved. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.11.07) | |
| A reaction: This appears to be a commitment by Hobbes to what we now call 'classical' mereology - that any bunch of things can count as a whole, whether they are together or dispersed. He seems to mean more than a watch surviving dismantling. |
| 17244 | To make a whole, parts needn't be put together, but can be united in the mind [Hobbes] |
| Full Idea: In composition, it is to be understood that for the making up of a whole there is no need of putting the parts together, so as to make them touch one another, but only of collecting them into one sum in the mind. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.07.08) | |
| A reaction: This seems to the 'unrestricted composition' of classical mereology, since it appears that Hobbes offers no restriction on which parts can be united by a mind, no matter how bizarre. |
| 17233 | Particulars contain universal things [Hobbes] |
| Full Idea: Universal things are contained in the nature of singular things. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 1.6.04) | |
| A reaction: That is the neatest and most accurate summary of the situation I have ever read. Particulars come first, but they are all riddled with generalities (but that is not as well said as Hobbes's remark). |
| 17246 | Some accidental features are permanent, unless the object perishes [Hobbes] |
| Full Idea: There are certain accidents which can never perish except the body perish also. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.08.03) | |
| A reaction: He is just making an observation, and not proposing a theory about essence. |
| 17251 | The feature which picks out or names a thing is usually called its 'essence' [Hobbes] |
| Full Idea: That accident for which we give a certain name to any body, or the accident which denominates its subject, is commonly called the essence thereof. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.08.23) | |
| A reaction: This is clearly a prelude to Locke's more carefully formulated 'nominal essence'. Fairly obvious, for nominalist empiricists. A bit surprising to say this was 'common'. |
| 17257 | It is the same river if it has the same source, no matter what flows in it [Hobbes] |
| Full Idea: That will be the same river which flows from one and the same fountain, whether the same water, or other water, or something other than water, flow thence. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.11.07) | |
| A reaction: This makes the source the one necessity for a river. I think the end matters too. If the Thames reversed direction, and flowed into Wales, it would not be the Thames any more. |
| 12853 | Some individuate the ship by unity of matter, and others by unity of form [Hobbes] |
| Full Idea: In the Ship of Theseus, some place individuity in the unity of matter; others, in the unity of form. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.11.07) | |
| A reaction: Simons raises this comment into a dogma, that there are at least two objects present in the ship. If I offered you a sum for the contents of your house, they would have a unity of monetary value. |
| 17256 | If a new ship were made of the discarded planks, would two ships be numerically the same? [Hobbes] |
| Full Idea: If some man kept the old planks as they were taken out, and by putting them afterwards together again in the same order, had again made a ship of them, ...there would have been two ships numerically the same, which is absurd. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.11.07) | |
| A reaction: This is the origin of the famous modern problematical example of the Ship of Theseus. The ancient example is just the case of whether you step into the same river, but using an artefact with parts, to make it clearer. |
| 16794 | As an infant, Socrates was not the same body, but he was the same human being [Hobbes] |
| Full Idea: It makes a great difference to ask concerning Socrates whether he is the same human being or whether he is the same body. For his body, when he is old, cannot be the same it was when he was an infant. …He can, however, be the same human being. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.11.07) | |
| A reaction: This is not commitment to full (Geachian) relative identity, but it notes the problem. |
| 17255 | Two bodies differ when (at some time) you can say something of one you can't say of the other [Hobbes] |
| Full Idea: Two bodies are said to differ from one another, when something may be said of one of them, which cannot be said of the other at the same time. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.11.02) | |
| A reaction: Note the astute addition of 'at the same time'. Note also that it is couched in terms of what is true, rather than in terms of 'properties' or 'accidents'. |
| 9723 | Sentences with 'if' are only conditionals if they can read as A-implies-B [Enderton] |
| Full Idea: Not all sentences using 'if' are conditionals. Consider 'if you want a banana, there is one in the kitchen'. The rough test is that a conditional can be rewritten as 'that A implies that B'. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.6.4) |
| 16582 | We can imagine a point swelling and contracting - but not how this could be done [Hobbes] |
| Full Idea: Even if we can feign in our mind that a point swells to a huge bulk and then contracts to a point - imagining something's made from nothing (ex nihilo), and nothing's made from something - still we cannot comprehend how this could be done in nature. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.08.20) | |
| A reaction: [compressed] Pasnau notes that this offers two sorts of conceivability, of something happening, and of a reason for it happening. A really nice idea, significant (I think) for scientific essentialists, who say possibilities are fewer than you think. |
| 17238 | Science aims to show causes and generation of things [Hobbes] |
| Full Idea: The end of science is the demonstration of the causes and generation of things. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 1.6.13) |
| 17260 | Imagination is just weakened sensation [Hobbes] |
| Full Idea: Imagination is nothing else but sense decaying or weakened by the absence of the object. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 4.25.07) | |
| A reaction: This sounds more like memory than imagination. He needs to say something about unusual combinations of memories, I would have thought. |
| 19373 | A 'conatus' is an initial motion, experienced by us as desire or aversion [Hobbes, by Arthur,R] |
| Full Idea: Hobbes' notion of 'conatus' is a 'beginning of motion' - a motion through a point of space in an instant of time. In a human subject this is experience as desire or aversion. It thus forms a bridge between physics and psychology. | |
| From: report of Thomas Hobbes (De Corpore (Elements, First Section) [1655], p.178) by Richard T.W. Arthur - Leibniz 3 'Worlds' | |
| A reaction: This sounds rather like the primitive concept of a power which I like, but the term seems to be used very vaguely, and never discussed carefully. The idea provoked Leibniz to connect physical force with mental life. |
| 2948 | Sensation is merely internal motion of the sentient being [Hobbes] |
| Full Idea: Sense in the sentient, can be nothing else but motion in some of the internal parts of the sentient; and the parts so moved are parts of the organs of sense. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 3.15.02) | |
| A reaction: Amazingly bold for the time, and presumably influenced by Lucretius. I am sympathetic, but to suggest that sensation is nothing more sounds a bit like a category mistake. Has he grasped that the brain is involved? |
| 17261 | Apart from pleasure and pain, the only emotions are appetite and aversion [Hobbes] |
| Full Idea: All the passions, called passions of the mind, consist of appetite and aversion, except pure pleasure and pain. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 4.25.13) | |
| A reaction: He now faces the challenge of explaining all the many other emotions in terms of these two. Good luck with that, Thomas. |
| 17236 | Words are not for communication, but as marks for remembering what we have learned [Hobbes] |
| Full Idea: The use of words consists in this, that they may serve for marks by which whatsoever we have found out may be recalled to memory ...but not as signs by which we declare the same to others. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 1.6.11) | |
| A reaction: This exactly fits the idea of mental files, of which I am a fan. That this is the actual purpose of language is an unusual but interesting view. |
| 16600 | Prime matter is body considered with mere size and extension, and potential [Hobbes] |
| Full Idea: Prime matter signifies body considered without the consideration of any form or accident except only magnitude or extension, and aptness to receive form and accidents. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.08.24) | |
| A reaction: I take 'considered without' to indicate that he thinks of it as a psychological abstraction, rather than some actual existing thing. |
| 17252 | Acting on a body is either creating or destroying a property in it [Hobbes] |
| Full Idea: A body is said to work upon or act, that is to say, do something to another body, when it either generates or destroys some accident in it. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.09.01) |
| 17254 | An effect needs a sufficient and necessary cause [Hobbes] |
| Full Idea: There can be no effect but from a sufficient and necessary cause. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.10.02) | |
| A reaction: To be compared with Mackie's subtler modern account of this matter. If two different separate causes could lead to the same result, it is hard to see how the cause must be 'necessary' (unless you say they lead to different effects). |
| 17235 | A cause is the complete sum of the features which necessitate the effect [Hobbes] |
| Full Idea: A cause it the sum or aggregate of all such accidents, both in the agents and in the patient, as concur to the producing of the effect propounded; all of which existing together, ti cannot be understood but that the effect existenth without them. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 1.6.10) | |
| A reaction: For most causes we meet, this definition will include gravity and electro-magnetism, so it doesn't help in narrowing things down. Notice that he accepts the necessity, despite his committed empiricism. |
| 17234 | Motion is losing one place and acquiring another [Hobbes] |
| Full Idea: Motion is privation of one place, and the acquisition of another. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 1.6.06) | |
| A reaction: This is basically the 'at-at' theory of motion which empiricists like, because it breaks motion down into atoms of experience. Hobbes needs an ontology which includes 'places'. |
| 17259 | 'Force' is the quantity of movement imposed on something [Hobbes] |
| Full Idea: I define 'force' to be the impetus or quickness of motion multiplied either into itself, or into the magnitude of the movent, by means of which whereof the said movent works more or less upon the body that resists it. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 3.15.02) | |
| A reaction: Not very helpful, perhaps, but it shows a view of force at quite an early date, well before Newton. |
| 17243 | Past times can't exist anywhere, apart from in our memories [Hobbes] |
| Full Idea: When people speak of the times of their predecessors, they do not think after their predecessors are gone that their times can be any where else than in the memory of those that remember. | |
| From: Thomas Hobbes (De Corpore (Elements, First Section) [1655], 2.07.03) |