23 ideas
| 19441 | All philosophies presuppose their historical moment, and arise from it [Feuerbach] |
| Full Idea: Every philosophy originates as a manifestation of its time; its origin presupposes its historical time. | |
| From: Ludwig Feuerbach (Towards a Critique of Hegel's Philosophy [1839], p.59) | |
| A reaction: There seems to be widespread agreement among continental philosophers about this idea, whereas analytic philosophers largely ignore, and treat Plato as if he were a current professor in Chicago. |
| 19442 | I don't study Plato for his own sake; the primary aim is always understanding [Feuerbach] |
| Full Idea: Plato in writing is only a means for me; that which is primary and a priori, that which is the ground to which all is ultimately referred, is understanding. | |
| From: Ludwig Feuerbach (Towards a Critique of Hegel's Philosophy [1839], p.63) | |
| A reaction: It always seems to that the main aim of philosophy is understanding - which is why its central activity is explanation. |
| 19444 | Each proposition has an antithesis, and truth exists as its refutation [Feuerbach] |
| Full Idea: Every intellectual determination has its antithesis, its contradiction. Truth exists not in unity with, but in refutation of its opposite. | |
| From: Ludwig Feuerbach (Towards a Critique of Hegel's Philosophy [1839], p.72) | |
| A reaction: This appears to be a rejection of the 'synthesis' in Hegel, in favour of what strikes me as a rather more sensible interpretation of the modern dialectic. Being exists in contrast to nothingness, and truth exists in contrast to its negation? |
| 19445 | A dialectician has to be his own opponent [Feuerbach] |
| Full Idea: A thinker is a dialectician only insofar as he is his own opponent. | |
| From: Ludwig Feuerbach (Towards a Critique of Hegel's Philosophy [1839], p.72) | |
| A reaction: Quite an inspirational slogan for beginners in philosophy. How many non-philosophers are willing to be their own opponent. In law courts and the House of Commons we assign the roles to separate persons. Hence rhetoric replaces reason? |
| 19443 | Truth forges an impersonal unity between people [Feuerbach] |
| Full Idea: The urge to communicate is a fundamental urge - the urge for truth. ...That which is true belongs neither to me nor exclusively to you, but is common to all. The thought in which 'I' and 'You' are united is a true thought. | |
| From: Ludwig Feuerbach (Towards a Critique of Hegel's Philosophy [1839], p.65) | |
| A reaction: Sceptics may doubt that there are such truths, but this is certainly how we experience agreement - that there is some truth shared between us which is no longer the possession of either of us. Nice idea. |
| 22271 | Aristotle was the first to use schematic letters in logic [Aristotle, by Potter] |
| Full Idea: It was Aristotle who initiated the use of the letter of the (Greek) alphabet 'schematically', to stand for an unspecified piece of language of some appropriate grammatical type. | |
| From: report of Aristotle (Prior Analytics [c.328 BCE]) by Michael Potter - The Rise of Analytic Philosophy 1879-1930 02 'Aris' | |
| A reaction: Did he invent it from scratch, or borrow it from the mathematicians? Euclid labels diagrams with letters. |
| 11060 | Aristotelian syllogisms are three-part, subject-predicate, existentially committed, with laws of thought [Aristotle, by Hanna] |
| Full Idea: Aristotle's logic is based on the triadic syllogism, the distinction between subject and one-place predicates, that universal claims have existential commitment, and bivalence, excluded middle and noncontradiction. | |
| From: report of Aristotle (Prior Analytics [c.328 BCE]) by Robert Hanna - Rationality and Logic 2.2 |
| 18909 | Aristotelian sentences are made up by one of four 'formative' connectors [Aristotle, by Engelbretsen] |
| Full Idea: For Aristotle there are four formatives for sentences: 'belongs to some', 'belongs to every', 'belongs to no', and 'does not belong to every'. These are 'copulae'. Aristotle would have written 'wise belongs to some man'. | |
| From: report of Aristotle (Prior Analytics [c.328 BCE]) by George Engelbretsen - Trees, Terms and Truth 3 | |
| A reaction: A rather set-theoretic reading. This invites a Quinean scepticism about whether wisdom is some entity which can 'belong' to a person. It makes trope theory sound attractive, offering a unique wisdom that is integrated into that particular person. |
| 8080 | Aristotelian identified 256 possible syllogisms, saying that 19 are valid [Aristotle, by Devlin] |
| Full Idea: Aristotle identified four 'figures' of argument, based on combinations of Subject (S) and Predicate (P) and Middle term (M). The addition of 'all' and 'some', and 'has' and 'has not' got the property, resulted in 256 possible syllogisms, 19 of them valid. | |
| From: report of Aristotle (Prior Analytics [c.328 BCE]) by Keith Devlin - Goodbye Descartes Ch.2 | |
| A reaction: [Compressed version of Devlin] What Aristotle did was astonishing, and must be one of the key ideas of western civilization, even though a lot of his assumptions have been revised or rejected. |
| 13912 | Aristotle replaced Plato's noun-verb form with unions of pairs of terms by one of four 'copulae' [Aristotle, by Engelbretsen/Sayward] |
| Full Idea: Aristotle replaced the Platonic noun-verb account of logical syntax with a 'copular' account. A sentence is a pair of terms bound together logically (not necessarily grammatically) by one of four 'logical copulae' (every, none, some, not some). | |
| From: report of Aristotle (Prior Analytics [c.328 BCE]) by Engelbretsen,G/Sayward,C - Philosophical Logic: Intro to Advanced Topics 8 | |
| A reaction: So the four copulas are are-all, are-never, are-sometimes, and are-sometime-not. Consider 'men' and 'mortal'. Alternatively, Idea 18909. |
| 8071 | Aristotle listed nineteen valid syllogisms (though a few of them were wrong) [Aristotle, by Devlin] |
| Full Idea: Aristotle listed a total of nineteen syllogisms involved in logical reasoning, though some of the ones on his list were subsequently shown to be invalid. | |
| From: report of Aristotle (Prior Analytics [c.328 BCE], Ch.1) by Keith Devlin - Goodbye Descartes | |
| A reaction: It is quite upsetting to think that the founding genius got some of it wrong, but that just shows how subtle and complex the analysis of rational thought can be. |
| 13819 | Aristotle's said some Fs are G or some Fs are not G, forgetting that there might be no Fs [Bostock on Aristotle] |
| Full Idea: Aristotle's system accepted as correct some laws which nowadays we reject, for example |= (Some Fs are G) or (some Fs are not G). He failed to take into account the possibility of there being no Fs at all. | |
| From: comment on Aristotle (Prior Analytics [c.328 BCE]) by David Bostock - Intermediate Logic 8.4 |
| 9403 | There are three different deductions for actual terms, necessary terms and possible terms [Aristotle] |
| Full Idea: Since to belong, to belong of necessity, and to be possible to belong are different, ..there will be different deductions for each; one deduction will be from necessary terms, one from terms which belong, and one from possible terms. | |
| From: Aristotle (Prior Analytics [c.328 BCE], 29b29-35) | |
| A reaction: Fitting and Mendelsohn cite this as the earliest thoughts on modal logic. but Kneale and Kneale say that Aristotle got into a muddle, and so was unable to create a workable system. |
| 11148 | Deduction is when we suppose one thing, and another necessarily follows [Aristotle] |
| Full Idea: A deduction is a discourse in which, certain things having been supposed, something different from the things supposed results of necessity because these things are so. | |
| From: Aristotle (Prior Analytics [c.328 BCE], 24b18) | |
| A reaction: Notice that it is modal ('suppose', rather than 'know'), that necessity is involved, which is presumably metaphysical necessity, and that there are assumptions about what would be true, and not just what follows from what. |
| 18896 | Aristotle places terms at opposite ends, joined by a quantified copula [Aristotle, by Sommers] |
| Full Idea: Aristotle often preferred to formulate predications by placing the terms at opposite ends of the sentence and joining them by predicating expressions like 'belongs-to-some' or 'belongs-to-every'. | |
| From: report of Aristotle (Prior Analytics [c.328 BCE]) by Fred Sommers - Intellectual Autobiography 'Conceptions' | |
| A reaction: This is Sommers's picture of Aristotle, which led Sommers to develop his modern Term Logic. |
| 3300 | Aristotle's logic is based on the subject/predicate distinction, which leads him to substances and properties [Aristotle, by Benardete,JA] |
| Full Idea: Basic to Aristotle's logic is the grammatical distinction between subject and predicate, which he glosses in terms of the contrast between a substance and its properties. | |
| From: report of Aristotle (Prior Analytics [c.328 BCE]) by José A. Benardete - Metaphysics: the logical approach Intro | |
| A reaction: The introduction of quantifiers and 'logical form' can't disguise the fact that we still talk about (and with) objects and predicates, because no one can think of any other way to talk. |
| 11149 | Affirming/denying sentences are universal, particular, or indeterminate [Aristotle] |
| Full Idea: Affirming/denying sentences are universal, particular, or indeterminate. Belonging 'to every/to none' is universal; belonging 'to some/not to some/not to every' is particular; belonging or not belonging (without universal/particular) is indeterminate. | |
| From: Aristotle (Prior Analytics [c.328 BCE], 24a16) |
| 8079 | Aristotelian logic has two quantifiers of the subject ('all' and 'some') [Aristotle, by Devlin] |
| Full Idea: Aristotelian logic has two quantifiers of the subject ('all' and 'some'), and two ways to combine the subject with the predicate ('have', and 'have not'), giving four propositions: all-s-have-p, all-s-have-not-p, some-s-have-p, and some-s-have-not-p. | |
| From: report of Aristotle (Prior Analytics [c.328 BCE]) by Keith Devlin - Goodbye Descartes Ch.2 | |
| A reaction: Frege seems to have switched from 'some' to 'at-least-one'. Since then other quantifiers have been proposed. See, for example, Ideas 7806 and 6068. |
| 19446 | To our consciousness it is language which looks unreal [Feuerbach] |
| Full Idea: To sensuous consciousness it is precisely language that is unreal, nothing. | |
| From: Ludwig Feuerbach (Towards a Critique of Hegel's Philosophy [1839], p.77) | |
| A reaction: Offered as a corrective to the view that our ontological commitments entirely concern what we are willing to say. |
| 14641 | A deduction is necessary if the major (but not the minor) premise is also necessary [Aristotle] |
| Full Idea: It sometimes results that the deduction becomes necessary when only one of the premises is necessary (not whatever premise it might be, however, but only the premise in relation to the major extreme [premise]). | |
| From: Aristotle (Prior Analytics [c.328 BCE], 30a15) | |
| A reaction: The qualification is brackets is said by Plantinga (1969) to be a recognition of the de re/ de dicto distinction (later taken up by Aquinas). Plantinga gives two examples to illustrate his reading. |
| 19447 | The Absolute is the 'and' which unites 'spirit and nature' [Feuerbach] |
| Full Idea: The Absolute is spirit and nature. ...But what then is the Absolute? Nothing other than this 'and', that is, the unity of spirit and nature. | |
| From: Ludwig Feuerbach (Towards a Critique of Hegel's Philosophy [1839], p.82) | |
| A reaction: This is Feuerbach's spin on Hegel. He has been outlining idealist philosophy and the philosophy of nature in Schelling. Is this Spinoza's one substance? |
| 18911 | Linguistic terms form a hierarchy, with higher terms predicable of increasing numbers of things [Aristotle, by Engelbretsen] |
| Full Idea: According to Aristotle, the terms of a language form a finite hierarchy, where the higher terms are predicable of more things than are lower terms. | |
| From: report of Aristotle (Prior Analytics [c.328 BCE]) by George Engelbretsen - Trees, Terms and Truth 3 | |
| A reaction: I would be a bit cautious about placing something precisely in a hierarchy according to how many things it can be predicated of. It is a start, though, in trying to give a decent account of generality, which is a major concept in philosophy. |
| 4871 | A thing is free if it acts only by the necessity of its own nature [Spinoza] |
| Full Idea: I say that a thing is free, which exists and acts solely by the necessity of its own nature. | |
| From: Baruch de Spinoza (Letter to G.H. Schaller [1674], 1674.10) | |
| A reaction: Of course, this isn't 'freedom' at all, but it seems to exactly right as an account of so-called freedom. In the case of a human being the 'necessity of our own nature' is character, and virtue and vice are the expressions of the necessities of character. |