25 ideas
| 2098 | The principle of sufficient reason is needed if we are to proceed from maths to physics [Leibniz] |
| Full Idea: In order to proceed from mathematics to physics the principle of sufficient reason is necessary, that nothing happens without there being a reason why it should be thus rather than otherwise. | |
| From: Gottfried Leibniz (Letters to Samuel Clarke [1716], §2) |
| 3646 | There is always a reason why things are thus rather than otherwise [Leibniz] |
| Full Idea: Nothing happens without a sufficient reason why it should be thus rather than otherwise. | |
| From: Gottfried Leibniz (Letters to Samuel Clarke [1716], 3.2) |
| 2104 | No reason could limit the quantity of matter, so there is no limit [Leibniz] |
| Full Idea: There is no possible reason which could limit the quantity of matter; therefore there cannot in fact be any such limitation. | |
| From: Gottfried Leibniz (Letters to Samuel Clarke [1716], 4.21) |
| 6396 | A sentence is held true because of a combination of meaning and belief [Davidson] |
| Full Idea: A sentence is held true because of two factors: what the holder takes the sentence to mean, and what he believes. | |
| From: Donald Davidson (Thought and Talk [1975], p.20) | |
| A reaction: A key question is whether a belief (e.g. an imagistic one, or one held by an animal) could be true, even though no sentence is involved. Linguistic philosophers tend to avoid this question, or assume the answer is 'no'. |
| 19385 | All simply substances are in harmony, because they all represent the one universe [Leibniz] |
| Full Idea: All simple substances will always have a harmony among themselves, because they always represent the same universe. | |
| From: Gottfried Leibniz (Letters to Samuel Clarke [1716], V §91), quoted by Richard T.W. Arthur - Leibniz | |
| A reaction: We can accept that the universe itself does not contain contradictions (how could it), but it is a leap of faith to say that all monads represent the universe well enough to avoid contradictions. Maps can contradict one another. |
| 21346 | The ratio between two lines can't be a feature of one, and cannot be in both [Leibniz] |
| Full Idea: If the ratio of two lines L and M is conceived as abstracted from them both, without considering which is the subject and which the object, which will then be the subject? We cannot say both, for then we should have an accident in two subjects. | |
| From: Gottfried Leibniz (Letters to Samuel Clarke [1716], 5th Paper, §47), quoted by John Heil - Relations 'External' | |
| A reaction: [compressed] Leibniz is rejecting external relations as having any status in ontology. It looks like a mistake (originating in Aristotle) to try to shoehorn the ontology of relations into the substance-properties framework. |
| 11145 | Having a belief involves the possibility of being mistaken [Davidson] |
| Full Idea: Someone cannot have a belief unless he understands the possibility of being mistaken. | |
| From: Donald Davidson (Thought and Talk [1975], p.170) | |
| A reaction: If you pretend to throw a ball for a dog, but don't release it, the dog experiences being mistaken very dramatically. |
| 6397 | The concept of belief can only derive from relationship to a speech community [Davidson] |
| Full Idea: We have the idea of belief from its role in the interpretation of language; as a private attitude it is not intelligible except in relation to public language. So a creature must be a member of a speech community to have the concept of belief. | |
| From: Donald Davidson (Thought and Talk [1975], p.22) | |
| A reaction: This shows how Wittgenstein's Private Language Argument (e.g. Idea 4152) hovers behind Davidson's philosophy. The idea is quite persuasive. A solitary creature just follows its mental states. The question of whether it believes them is a meta-thought. |
| 6392 | Thought depends on speech [Davidson] |
| Full Idea: The thesis I want to refine and then argue for is that thought depends on speech. | |
| From: Donald Davidson (Thought and Talk [1975], p.8) | |
| A reaction: This has the instant and rather implausible implication that animals don't think. He is not, of course, saying that all thought is speech, which would leave out thinking in images. You can't do much proper thought without concepts and propositions. |
| 6393 | A creature doesn't think unless it interprets another's speech [Davidson] |
| Full Idea: A creature cannot have a thought unless it is an interpreter of the speech of another. | |
| From: Donald Davidson (Thought and Talk [1975], p.9) | |
| A reaction: His use of the word 'creature' shows that he is perfectly aware of the issue of whether animals think, and he is, presumably, denying it. At first glance this sounds silly, but maybe animals don't really 'think', in our sense of the word. |
| 11144 | Concepts are only possible in a language community [Davidson] |
| Full Idea: A private attitude is not intelligible except as an adjustment to the public norms provided by language. It follows that a creature must be a member of speech community if it is to have the concept of belief. | |
| From: Donald Davidson (Thought and Talk [1975], p.170) | |
| A reaction: This obviously draws on Wittgenstein's private language argument, and strikes me as blatantly wrong, because I take higher animals to have concepts without language. Pure vision gives rise to concepts. I don't even think they are necessarily conscious. |
| 6395 | An understood sentence can be used for almost anything; it isn't language if it has only one use [Davidson] |
| Full Idea: Once a sentence is understood, an utterance of it may be used to serve almost any extra-linguistic purpose; an instrument that could be put to only one use would lack autonomy of meaning, which means it should not be counted as language. | |
| From: Donald Davidson (Thought and Talk [1975], p.17) | |
| A reaction: I find this point very appealing, in opposition to the Wittgenstein view of meaning as use. Passwords seem to me a striking case of the separation of meaning and use. I like the phrase 'autonomy of meaning'. Random sticks can form a word. |
| 6394 | The pattern of sentences held true gives sentences their meaning [Davidson] |
| Full Idea: Although most utterances are not concerned with truth, it is the pattern of sentences held true that gives sentences their meaning. | |
| From: Donald Davidson (Thought and Talk [1975], p.14) | |
| A reaction: Davidson's distinctive version of meaning holism, as opposed to Quine's rather behaviouristic version. I agree that we relate to people through the pattern of sentences they hold true, but I am unconvinced that this 'gives sentences their meaning'. |
| 13304 | Learned men gain more in one day than others do in a lifetime [Posidonius] |
| Full Idea: In a single day there lies open to men of learning more than there ever does to the unenlightened in the longest of lifetimes. | |
| From: Posidonius (fragments/reports [c.95 BCE]), quoted by Seneca the Younger - Letters from a Stoic 078 | |
| A reaction: These remarks endorsing the infinite superiority of the educated to the uneducated seem to have been popular in late antiquity. It tends to be the religions which discourage great learning, especially in their emphasis on a single book. |
| 2106 | The only simple things are monads, with no parts or extension [Leibniz] |
| Full Idea: According to me there is nothing simple except true monads, which have no parts and no extensions. | |
| From: Gottfried Leibniz (Letters to Samuel Clarke [1716], 5.24) |
| 2102 | Atomism is irrational because it suggests that two atoms can be indistinguishable [Leibniz] |
| Full Idea: There are no two individuals indiscernible from one another - leaves, or drops of water, for example. This is an argument against atoms, which, like the void, are opposed to the principles of a true metaphysic. | |
| From: Gottfried Leibniz (Letters to Samuel Clarke [1716], 4.04) |
| 2105 | Things are infinitely subdivisible and contain new worlds, which atoms would make impossible [Leibniz] |
| Full Idea: The least corpuscle is actually subdivided ad infinitum and contains a world of new created things, which this universe would lack if this corpuscle were an atom. | |
| From: Gottfried Leibniz (Letters to Samuel Clarke [1716], 4.PS) |
| 20965 | Leibniz upheld conservations of momentum and energy [Leibniz, by Papineau] |
| Full Idea: In place of Descartes's conservation of 'quantity of motion', Leibniz upheld both the conservation of linear momentum and the conservation of kinetic energy. | |
| From: report of Gottfried Leibniz (Letters to Samuel Clarke [1716], 5th paper) by David Papineau - Thinking about Consciousness App 2 | |
| A reaction: The point is that momentum involves velocity (which includes direction) rather than speed. Leibniz more or less invented the concept of 'energy' ('vis viva'). Papineau says these two leave no room for causation by mental substance. |
| 2103 | The idea that the universe could be moved forward with no other change is just a fantasy [Leibniz] |
| Full Idea: To say that God could cause the universe to move forward in a straight line or otherwise without changing it in any other way is another fanciful supposition. | |
| From: Gottfried Leibniz (Letters to Samuel Clarke [1716], 4.14) |
| 2100 | Space and time are purely relative [Leibniz] |
| Full Idea: I have more than once stated that I held space to be something purely relative, like time. | |
| From: Gottfried Leibniz (Letters to Samuel Clarke [1716], 3.4) |
| 20820 | Time is an interval of motion, or the measure of speed [Posidonius, by Stobaeus] |
| Full Idea: Posidonius defined time thus: it is an interval of motion, or the measure of speed and slowness. | |
| From: report of Posidonius (fragments/reports [c.95 BCE]) by John Stobaeus - Anthology 1.08.42 | |
| A reaction: Hm. Can we define motion or speed without alluding to time? Looks like we have to define them as a conjoined pair, which means we cannot fully understand either of them. |
| 2107 | No time exists except instants, and instants are not even a part of time, so time does not exist [Leibniz] |
| Full Idea: How could a thing exist, no part of which ever exists? In the case of time, nothing exists but instants, and an instant is not even a part of time. | |
| From: Gottfried Leibniz (Letters to Samuel Clarke [1716], 5.49) |
| 2101 | If everything in the universe happened a year earlier, there would be no discernible difference [Leibniz] |
| Full Idea: To ask why God did not make everything a year sooner would be reasonable if time were something apart from temporal things, but time is just the succession of things, which remains the same if the universe is created a year sooner. | |
| From: Gottfried Leibniz (Letters to Samuel Clarke [1716], 3.6) |
| 22894 | If time were absolute that would make God's existence dependent on it [Leibniz, by Bardon] |
| Full Idea: Leibniz argues that if time is a thing in itself, and God is 'in' time, then God would be dependent for His existence on the existence of time. | |
| From: report of Gottfried Leibniz (Letters to Samuel Clarke [1716]) by Adrian Bardon - Brief History of the Philosophy of Time 3 'Newton' | |
| A reaction: Hence Leibniz says time is merely relations between events. Not sure what he thinks an event is. What is God made of? Is there some divine matter upon which God's existence must depend? |
| 2099 | The existence of God, and all metaphysics, follows from the Principle of Sufficient Reason [Leibniz] |
| Full Idea: By this principle alone, that there must be a sufficient reason why things are thus rather than otherwise, I prove the existence of the Divinity, and all the rest of metaphysics or natural theology. | |
| From: Gottfried Leibniz (Letters to Samuel Clarke [1716], §2) |