| 430 | Senses are no use if the soul is corrupt [Heraclitus] |
| Full Idea: The eyes and ears are bad witnesses for men if they have barbarian souls. | |
| From: Heraclitus (fragments/reports [c.500 BCE], B107), quoted by Sextus Empiricus - Against the Mathematicians 7.126 |
| 3058 | Only reason can prove the truth of facts [Parmenides] |
| Full Idea: Reason alone will prove the truth of facts. | |
| From: Parmenides (fragments/reports [c.474 BCE]), quoted by Diogenes Laertius - Lives of Eminent Philosophers 09.3.3 |
| 20897 | Obscure knowledge belongs to the five senses, and genuine knowledge is the other type [Democritus] |
| Full Idea: There are two forms of knowledge [gnomé], the one genuine, the other obscure. And to the obscure one belongs all of these: sight, hearing, smell, taste, touch. The other is genuine, and is separated from this one. | |
| From: Democritus (fragments/reports [c.431 BCE], B011), quoted by Sextus Empiricus - Against the Logicians (two books) 7.139 | |
| A reaction: [Sextus goes on to make it clear that the 'genuine' one is knowledge acquired by thought]. I take Parmenides to be the first rationalist. It is interesting that Democritus, who devoted his life to finding causal explanations, seems to be a rationalist. |
| 517 | All evidence comes from senses, so they are indispensable to the mind [Democritus] |
| Full Idea: Mind must never reject the senses, because that is where it gets its evidence, and it would be the mind's downfall. | |
| From: Democritus (fragments/reports [c.431 BCE], B125), quoted by Galen - On Medical Experience 15.8 |
| 151 | True knowledge is of the reality behind sense experience [Plato] |
| Full Idea: True knowledge is concerned with the abode of true reality, without colour or shape, intangible but utterly real, apprehensible only to the intellect. | |
| From: Plato (Phaedrus [c.366 BCE], 247c) |
| 2162 | If theory and practice conflict, the best part of the mind accepts theory, so the other part is of lower grade [Plato] |
| Full Idea: When appearance and measure conflict…it is the best part of the mind which accepts measurements and calculations, and the part which opposes them, therefore, must be a low-grade part of the mind. | |
| From: Plato (The Republic [c.374 BCE], 603a) |
| 1637 | A soul without understanding is ugly [Plato] |
| Full Idea: The soul that lacks understanding must be set down as ugly. | |
| From: Plato (The Sophist [c.359 BCE], 228d) | |
| A reaction: The teleological view of things understands their nature in things of their perfection. and the essence of beauty is perfection. It is the mind's nature to know. Failing to know is as ugly as allowing your crops to die. |
| 2068 | With what physical faculty do we perceive pairs of opposed abstract qualities? [Plato] |
| Full Idea: With what physical faculty do we perceive being and not-being, similarity and dissimilarity, identity and difference, oneness and many, odd and even and other maths, ….fineness and goodness? | |
| From: Plato (Theaetetus [c.368 BCE], 185d) |
| 2069 | Thought must grasp being itself before truth becomes possible [Plato] |
| Full Idea: If you can't apprehend being you can't apprehend truth, and so a thing could not be known. Therefore knowledge is not located in immediate experience but in thinking about it, since the latter makes it possible to grasp being and truth. | |
| From: Plato (Theaetetus [c.368 BCE], 186c) |
| 2078 | You might mistake eleven for twelve in your senses, but not in your mind [Plato] |
| Full Idea: Sight or touch might make someone take eleven for twelve, but he could never form this mistaken belief about the contents of his mind. | |
| From: Plato (Theaetetus [c.368 BCE], 195e) |
| 334 | Only bird-brained people think astronomy is entirely a matter of evidence [Plato] |
| Full Idea: Birds are empty-headed men who grew feathers instead of hair, because they were interested in astronomy but thought it was entirely a matter of physical evidence. | |
| From: Plato (Timaeus [c.349 BCE], 91d) |
| 1726 | We may think when we wish, but not perceive, because universals are within the mind [Aristotle] |
| Full Idea: Perception is of particular things, but knowledge is of universals, which are in a way in the soul itself. Thus a man may think whenever he wishes, but not perceive. | |
| From: Aristotle (De Anima [c.329 BCE], 417b22) |
| 23312 | Aristotle is a rationalist, but reason is slowly acquired through perception and experience [Aristotle, by Frede,M] |
| Full Idea: Aristotle is a rationalist …but reason for him is a disposition which we only acquire over time. Its acquisition is made possible primarily by perception and experience. | |
| From: report of Aristotle (works [c.330 BCE]) by Michael Frede - Aristotle's Rationalism p.173 | |
| A reaction: I would describe this process as the gradual acquisition of the skill of objectivity, which needs the right knowledge and concepts to evaluate new experiences. |
| 22748 | Some say motion is perceived by sense, but others say it is by intellect [Sext.Empiricus] |
| Full Idea: Some assert that motion is perceived by sense, but others that it is not perceived at all by sense but by the intellect through sensation. | |
| From: Sextus Empiricus (Against the Physicists (two books) [c.180], II.062) | |
| A reaction: Descartes' wax argument defends the idea that change is perceived by intellect. The intellect has to distinguish the relative aspect of each motion, such as when someone is walking around on a moving ship. Even sense also need memory. |
| 22117 | Our minds grasp reality by direct illumination (rather than abstraction from experience) [Augustine, by Matthews] |
| Full Idea: Instead of supposing that what we know can be abstracted from sensible particulars that instantiate such knowledge, Augustine insists that our mind is so constituted as to see 'intelligible realities' directly by inner illumination. | |
| From: report of Augustine (works [c.415]) by Gareth B. Matthews - Augustine p.74 | |
| A reaction: His 'theory of illumination'. This seems to be a sort of super-rationalism. This doesn't make clear the role of sensations. Surely he doesn't thing that we just bypass them? |
| 20224 | Sensation prepares the way for intellectual knowledge, which needs the virtues of reason [Aquinas] |
| Full Idea: Knowledge of truth is not consummated in the sensitive powers of apprehension, for these prepare the way to intellectual knowledge. And therefore in these powers there are none of the virtues by which we know truth; these are in the intellect or reason. | |
| From: Thomas Aquinas (Summa Theologicae [1265], I-II Q56 a5 obj3), quoted by Linda Trinkaus Zagzebski - Virtues of the Mind III 2.2 | |
| A reaction: A gem of a quotation for Zagzebski's thesis, that knowledge is defined in terms of the intellectual virtues. The only virtues of perception are in focusing and paying attention to features. Good eyesight is a biological 'virtue', I suppose. |
| 3611 | Understanding, rather than imagination or senses, gives knowledge [Descartes] |
| Full Idea: Neither our imagination nor our senses could ever assure us of anything, if our understanding did not intervene. | |
| From: René Descartes (A Discourse on Method [1637], §4.37) |
| 2263 | The wax is not perceived by the senses, but by the mind alone [Descartes] |
| Full Idea: The perception of the wax is neither a seeing, nor a touching, nor an imagining. Rather, it is an inspection on the part of the mind alone. | |
| From: René Descartes (Meditations [1641], §2.31) |
| 3627 | Dogs can make the same judgements as us about variable things [Gassendi on Descartes] |
| Full Idea: A dog certainly makes similar kinds of judgement to your perceiving men by their hats and cloaks when they see their master's hat or clothes, …and they can recognise their master even if he is standing, sitting, lying down, or crouching. | |
| From: comment on René Descartes (Meditations [1641], §2.32) by Pierre Gassendi - Objections to 'Meditations' (Fifth) 272 |
| 2264 | We don't 'see' men in heavy clothes, we judge them to be men [Descartes] |
| Full Idea: Were I to look out of my window and observe men crossing the square, I would ordinarily say that I see the men themselves. But what do I see but hats and clothes, which could conceal automata? Yet I judge them to be men. | |
| From: René Descartes (Meditations [1641], §2.32) |
| 2265 | We perceive objects by intellect, not by senses or imagination [Descartes] |
| Full Idea: Bodies are not, properly speaking, perceived by the senses or by the faculty of imagination, but by the intellect alone. | |
| From: René Descartes (Meditations [1641], §2.34) |
| 22011 | The first principles of truth are not rational, but are known by the heart [Pascal] |
| Full Idea: We know the truth not only through our reason but also through our heart. It is through that latter that we know first principles, and reason, which has nothing to do with it, tries in vain to refute them. | |
| From: Blaise Pascal (Pensées [1662], 110 p.58), quoted by Terry Pinkard - German Philosophy 1760-1860 04 n4 | |
| A reaction: This resembles the rationalist defence of fundamental a priori principles, needed as a foundation for knowledge. But the a priori insights are not a feature of the 'natural light' of reason, and are presumably inexplicable (of the 'heart'). |
| 4865 | The eyes of the mind are proofs [Spinoza] |
| Full Idea: The eyes of the mind … are none other than proofs. | |
| From: Baruch de Spinoza (The Ethics [1675], V Pr 23) | |
| A reaction: A wonderful slogan for rationalists! Technically it sounds a bit dodgy, as steps seem to be required for a proof, whereas the eyes of the mind presumably offer a priori intuitions, or clear and distinct conceptions. In essence, he is right. |
| 2110 | We all expect the sun to rise tomorrow by experience, but astronomers expect it by reason [Leibniz] |
| Full Idea: When we expect it to be day tomorrow, we all behave as empiricists, because until now it has always happened thus. The astronomer alone knows this by reason. | |
| From: Gottfried Leibniz (Monadology [1716], §28) |
| 4302 | You may experience a universal truth, but only reason can tell you that it is always true [Leibniz] |
| Full Idea: However often one experiences instances of a universal truth, one could never know inductively that it would always hold unless one knew through reason that it was necessary. | |
| From: Gottfried Leibniz (New Essays on Human Understanding [1704], 1.01) | |
| A reaction: The problem, though, is that as soon as we go beyond experience we are not very reliable, and are liable to arrogance, error and lack of imagination. |
| 12930 | The senses are confused, and necessities come from distinct intellectual ideas [Leibniz] |
| Full Idea: Intellectual ideas, from which necessary truths arise, do not come from the senses. ...The ideas that come from the senses are confused; and so too, at least in part, are the truths which depend on them, whereas intellectual ideas are distinct. | |
| From: Gottfried Leibniz (New Essays on Human Understanding [1704], 1.01) | |
| A reaction: One might compare Descartes' example of the chiliagon, which is only grasped clearly by the intellect. However, the problem of vagueness seems to intrude as much into intellectual ideas as it does into the senses. He was a mathematician... |
| 12947 | We only believe in sensible things when reason helps the senses [Leibniz] |
| Full Idea: The senses could not convince us of the existence of sensible things without help from reason. | |
| From: Gottfried Leibniz (New Essays on Human Understanding [1704], 2.07) | |
| A reaction: This nicely pinpoints the big difficulty which keeps besetting orthodox empiricism. I've been educated as an empiricist, but I prefer Leibniz to Berkeley or Hume, and even to the more sensible Locke. |
| 5569 | We cannot represent objects unless we combine concepts with intuitions [Kant] |
| Full Idea: Understanding and sensibility can determine an object only in combination; if we separate them, then we have intuitions without concepts, or concepts without intuitions, but in either case representations that we cannot relate to any determinate objects. | |
| From: Immanuel Kant (Critique of Pure Reason [1781], B314/A258) | |
| A reaction: Although Kant seems to be rejecting the rationalist v empiricist debate, I take this to be evidence that Kant was a rationalist, because he thinks understanding cannot arise just from sensibility. |
| 19572 | Experiences tests reason, and reason tests experience [Novalis] |
| Full Idea: Experience is the test of the rational - and vice versa. | |
| From: Novalis (Miscellaneous Observations [1798], 010) | |
| A reaction: A wonderful remark. Surely we can't ignore our need to test claims of pure logic by filling in the variables with concrete instances, to assess validity? And philosophy without examples is doomed to be abstract waffle. Coherence is the combined aim. |
| 15625 | Sense perception is secondary and dependent, while thought is independent and primitive [Hegel] |
| Full Idea: What can be perceived by the senses is really secondary and not self-standing, while thoughts, on the contrary, are what is genuinely independent and primitive. | |
| From: Georg W.F.Hegel (Logic (Encyclopedia I) [1817], §41 Add2) | |
| A reaction: Although this is post-Kant, it strikes me as a perfect slogan for rationalism. Personally I would say that such a dichotomy is becoming a historical relic, in the light of modern understanding of the brain. Experience and thought are inextricable. |
| 21577 | Empirical truths are particular, so general truths need an a priori input of generality [Russell] |
| Full Idea: All empirical evidence is of particular truths. Hence, if there is any knowledge of general truths at all, there must be some knowledge of general truths which is independent of empirical evidence. | |
| From: Bertrand Russell (Our Knowledge of the External World [1914], 2) | |
| A reaction: Humean empiricists respond by being a sceptical of general truths. At this stage of his career Russell looks like a thoroughgoing rationalist, and he believes in the reality of universals, relations and propositions. He became more empirical later. |
| 5200 | The main claim of rationalism is that thought is an independent source of knowledge [Ayer] |
| Full Idea: The fundamental tenet of rationalism is that thought is an independent source of knowledge. | |
| From: A.J. Ayer (Language,Truth and Logic [1936], Ch.4) | |
| A reaction: Presumably one should add that thought gives synthetic knowledge. Thought is also an experience, so empiricists will always acknowledge that we could have some knowledge (of thought) by thought alone. |
| 4303 | The notion of substance lies at the heart of rationalist metaphysics [Cottingham] |
| Full Idea: The notion of substance lies at the heart of rationalist metaphysics. | |
| From: John Cottingham (The Rationalists [1988], p.75) | |
| A reaction: The idea of 'substance' has had an interesting revival in modern philosophy (though not, obviously, in physics). Maybe physics and philosophy have views of reality which are not complementary, but are rivals. |
| 8880 | In reducing arithmetic to self-evident logic, logicism is in sympathy with rationalism [Sosa] |
| Full Idea: In trying to reduce arithmetic to self-evident logical axioms, logicism is in sympathy with rationalism. | |
| From: Ernest Sosa (Beyond internal Foundations to external Virtues [2003], 6.7) | |
| A reaction: I have heard Frege called "the greatest of all rationalist philosophers". However, the apparent reduction of arithmetic to analytic truths played into the hands of logical positivists, who could then marginalise arithmetic. |
| 2504 | Rationalism can be based on an evolved computational brain with innate structure [Fodor] |
| Full Idea: Pinker's rationalism involves four main ideas: mind is a computational system, which is massively modular with a lot of innate structure resulting from evolution. | |
| From: Jerry A. Fodor (In a Critical Condition [2000], Ch.17) |
| 3704 | Moderate rationalists believe in fallible a priori justification [Bonjour] |
| Full Idea: Moderate rationalism preserves a priori justification, but rejects the idea that it is infallible. | |
| From: Laurence Bonjour (In Defence of Pure Reason [1998], §4.1) |
| 3707 | Our rules of thought can only be judged by pure rational insight [Bonjour] |
| Full Idea: Criteria or rules do not somehow apply to themselves. They must be judged by the sort of rational insight or intuition that the rationalist is advocating. | |
| From: Laurence Bonjour (In Defence of Pure Reason [1998], §5.2) |
| 2729 | Virtually all rationalists assert that we can have knowledge of synthetic a priori truths [Audi,R] |
| Full Idea: Rationalists virtually always assert or imply that, in addition to knowledge of analytic truths, there is knowledge of synthetic a priori truths. | |
| From: Robert Audi (Epistemology: contemporary introduction [1998], IV p.105) |
| 2741 | The principles of justification have to be a priori [Audi,R] |
| Full Idea: The crucial principles of justification are a priori. | |
| From: Robert Audi (Epistemology: contemporary introduction [1998], X p.311) |
| 8725 | Rationalism tries to apply mathematical methodology to all of knowledge [Shapiro] |
| Full Idea: Rationalism is a long-standing school that can be characterized as an attempt to extend the perceived methodology of mathematics to all of knowledge. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 1.1) | |
| A reaction: Sometimes called 'Descartes's Dream', or the 'Enlightenment Project', the dream of proving everything. Within maths, Hilbert's Programme aimed for the same certainty. Idea 22 is the motto for the opposition to this approach. |
| 17705 | Empiricists say rationalists mistake imaginative powers for modal insights [Mares] |
| Full Idea: Empiricist critiques of rationalism often accuse rationalists of confusing the limits of their imaginations with real insight into what is necessarily true. | |
| From: Edwin D. Mares (A Priori [2011], 03.01) | |
| A reaction: See ideas on 'Conceivable as possible' for more on this. You shouldn't just claim to 'see' that something is true, but be willing to offer some sort of reason, truthmaker or grounding. Without that, you may be right, but you are on weak ground. |
| 6576 | My view is 'circumspect rationalism' - that only our intellect can comprehend the world [Fogelin] |
| Full Idea: My own view might be called 'circumspect rationalism' - the view that our intellectual faculties provide our only means for comprehending the world in which we find oruselves. | |
| From: Robert Fogelin (Walking the Tightrope of Reason [2003], Ch.3) | |
| A reaction: He needs to say more than that to offer a theory, but I like the label, and it fits the modern revival of rationalism, with which I sympathise, and which rests, I think, on Russell's point that self-evidence comes in degrees, not as all-or-nothing truth. |