33 ideas
| 7113 | Phenomenology assumes that all consciousness is of something [Sartre] |
| Full Idea: The essential principle of phenomenology is that 'all consciousness is consciousness of something'. | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], I (B)) | |
| A reaction: This idea is found well before Husserl, in Schopenhauer (Idea 4166). It seems to contradict a thought such as Locke's (Idea 1202), that self-awareness is a separate and distinct criterion for personal identity. Sartre gives a nice account. |
| 10757 | Henkin semantics has a second domain of predicates and relations (in upper case) [Rossberg] |
| Full Idea: Henkin semantics (for second-order logic) specifies a second domain of predicates and relations for the upper case constants and variables. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §3) | |
| A reaction: This second domain is restricted to predicates and relations which are actually instantiated in the model. Second-order logic is complete with this semantics. Cf. Idea 10756. |
| 10759 | There are at least seven possible systems of semantics for second-order logic [Rossberg] |
| Full Idea: In addition to standard and Henkin semantics for second-order logic, one might also employ substitutional or game-theoretical or topological semantics, or Boolos's plural interpretation, or even a semantics inspired by Lesniewski. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §3) | |
| A reaction: This is helpful in seeing the full picture of what is going on in these logical systems. |
| 10751 | Second-order logic needs the sets, and its consequence has epistemological problems [Rossberg] |
| Full Idea: Second-order logic raises doubts because of its ontological commitment to the set-theoretic hierarchy, and the allegedly problematic epistemic status of the second-order consequence relation. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §1) | |
| A reaction: The 'epistemic' problem is whether you can know the truths, given that the logic is incomplete, and so they cannot all be proved. Rossberg defends second-order logic against the second problem. A third problem is that it may be mathematics. |
| 10753 | Logical consequence is intuitively semantic, and captured by model theory [Rossberg] |
| Full Idea: Logical consequence is intuitively taken to be a semantic notion, ...and it is therefore the formal semantics, i.e. the model theory, that captures logical consequence. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §2) | |
| A reaction: If you come at the issue from normal speech, this seems right, but if you start thinking about the necessity of logical consequence, that formal rules and proof-theory seem to be the foundation. |
| 10752 | Γ |- S says S can be deduced from Γ; Γ |= S says a good model for Γ makes S true [Rossberg] |
| Full Idea: Deductive consequence, written Γ|-S, is loosely read as 'the sentence S can be deduced from the sentences Γ', and semantic consequence Γ|=S says 'all models that make Γ true make S true as well'. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §2) | |
| A reaction: We might read |= as 'true in the same model as'. What is the relation, though, between the LHS and the RHS? They seem to be mutually related to some model, but not directly to one another. |
| 10754 | In proof-theory, logical form is shown by the logical constants [Rossberg] |
| Full Idea: A proof-theorist could insist that the logical form of a sentence is exhibited by the logical constants that it contains. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §2) | |
| A reaction: You have to first get to the formal logical constants, rather than the natural language ones. E.g. what is the truth table for 'but'? There is also the matter of the quantifiers and the domain, and distinguishing real objects and predicates from bogus. |
| 10756 | A model is a domain, and an interpretation assigning objects, predicates, relations etc. [Rossberg] |
| Full Idea: A standard model is a set of objects called the 'domain', and an interpretation function, assigning objects in the domain to names, subsets to predicate letters, subsets of the Cartesian product of the domain with itself to binary relation symbols etc. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §3) | |
| A reaction: The model actually specifies which objects have which predicates, and which objects are in which relations. Tarski's account of truth in terms of 'satisfaction' seems to be just a description of those pre-decided facts. |
| 10758 | If models of a mathematical theory are all isomorphic, it is 'categorical', with essentially one model [Rossberg] |
| Full Idea: A mathematical theory is 'categorical' if, and only if, all of its models are isomorphic. Such a theory then essentially has just one model, the standard one. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §3) | |
| A reaction: So the term 'categorical' is gradually replacing the much-used phrase 'up to isomorphism'. |
| 10761 | Completeness can always be achieved by cunning model-design [Rossberg] |
| Full Idea: All that should be required to get a semantics relative to which a given deductive system is complete is a sufficiently cunning model-theorist. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §5) |
| 10755 | A deductive system is only incomplete with respect to a formal semantics [Rossberg] |
| Full Idea: No deductive system is semantically incomplete in and of itself; rather a deductive system is incomplete with respect to a specified formal semantics. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §3) | |
| A reaction: This important point indicates that a system might be complete with one semantics and incomplete with another. E.g. second-order logic can be made complete by employing a 'Henkin semantics'. |
| 7114 | The consciousness that says 'I think' is not the consciousness that thinks [Sartre] |
| Full Idea: The consciousness that says 'I think' is precisely not the consciousness that thinks. | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], I (B)) | |
| A reaction: All parties seem to be agreed that if we are going to introspect in search of our own ego, we must distinguish between the mental act of instrospection and the mental act of applying the mind to the world. Each gives a different result. |
| 7112 | The Cogito depends on a second-order experience, of being conscious of consciousness [Sartre] |
| Full Idea: We must remember that all authors who have described the Cogito have presented it as a reflective operation, i.e. as second-order. This Cogito is performed by a consciousness directed towards consciousness, which takes consciousness as its object. | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], I (B)) | |
| A reaction: Sartre is raising the nice question of whether the Cogito still works for first-order consciousness, which attends totally to external objects. He claims that it doesn't. Contrast Russell, who says (Idea 5380) that it only works when it is first-order! |
| 7119 | Is the Cogito reporting an immediate experience of doubting, or the whole enterprise of doubting? [Sartre] |
| Full Idea: When Descartes says 'I doubt therefore I am', is he talking about the spontaneous doubt that reflective consciousness grasps in its instantaneous character, or is he talking of the enterprise of doubting? This ambiguity can lead to serious errors. | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], II (B)) | |
| A reaction: Interesting. The obvious response is that it is about the immediate experience, but that leads to the problem of an instantaneous ego, which can't be justified over time. The 'enterprise' gives an enduring ego, but it is a more intellectual concept. |
| 7458 | The reliability of witnesses depends on whether they benefit from their observations [Laplace, by Hacking] |
| Full Idea: The credibility of a witness is in part a function of the story being reported. When the story claims to have infinite value, the temptation to lie for personal benefit is asymptotically infinite. | |
| From: report of Pierre Simon de Laplace (Philosophical Essay on Probability [1820], Ch.XI) by Ian Hacking - The Emergence of Probability Ch.8 | |
| A reaction: Laplace seems to especially have reports of miracles in mind. This observation certainly dashes any dreams one might have of producing a statistical measure of the reliability of testimony. |
| 7122 | We can never, even in principle, grasp other minds, because the Ego is self-conceiving [Sartre] |
| Full Idea: The Ego can be conceived only through itself and this is why we cannot grasp the consciousness of another (for this reason alone, and not because bodies separate us). | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], II (D)) | |
| A reaction: Interesting. This makes telepathy a logical impossibility, and the body the only possible route for the communication between two minds. But, is Sartre is right, how do bodily events penetrate the inturned world of the Ego? |
| 7125 | A consciousness can conceive of no other consciousness than itself [Sartre] |
| Full Idea: A consciousness can conceive of no other consciousness than itself. | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], Conc (1)) | |
| A reaction: This is why we don't know what it is like to be a bat. This seems right, though it looks like a contingent truth, and yet Sartre seems to offer it as a necessary truth. Can God conceive of my consciousness? |
| 7108 | The eternal truth of 2+2=4 is what gives unity to the mind which regularly thinks it [Sartre] |
| Full Idea: The unity of the thousand active consciousnesses through which I have added two and two to make four, is the transcendent object '2+2=4'. Without the permanence of this eternal truth, it would be impossible to conceive of a real unity of mind. | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], I (A)) | |
| A reaction: This is the germ of externalism, here presented as a Platonic attitude to arithmetic, rather than being about water or gold. He claims that internalist attitudes to unity are fictions. I am inclined to think he is wrong, and that unity is biological. |
| 7111 | Consciousness exists as consciousness of itself [Sartre] |
| Full Idea: The existence of consciousness is an absolute, because consciousness is consciousness of itself; the type of existence that consciousness has is that it is consciousness of itself. | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], I (A)) | |
| A reaction: I find this unconvincing. Anyone analysis the nature of the mind should think as much about animal minds as human minds. It seems obvious to me that there is likely to be an animal consciousness which is entirely of environment and its body. |
| 22226 | Since we are a consciousness, Sartre entirely rejected the unconscious mind [Sartre, by Daigle] |
| Full Idea: Sartre refused, denied and fought against the unconscious. Since we are consciousness, there cannot be such a thing as unconsciousness. | |
| From: report of Jean-Paul Sartre (Transcendence of the Ego [1937]) by Christine Daigle - Jean-Paul Sartre 2.1 | |
| A reaction: The modern view is increasingly opposed to this, as neuroscience and psychology uncover hidden motives etc. Sartre's view is still legitimate, though. An unconscious motive is not more my motive than a law of the land is part of me? |
| 7107 | Intentionality defines, transcends and unites consciousness [Sartre] |
| Full Idea: Consciousness is defined by intentionality. Through intentionality it transcends itself, it unifies itself by going outside itself. | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], I (A)) | |
| A reaction: The standard view for a hundred years was Brentano's idea that intentionality defines the mind. Qualia are the modern rival. If I had to choose I think I would go for intentionality, but they may be naturally and metaphysically inseparable. |
| 7109 | If you think of '2+2=4' as the content of thought, the self must be united transcendentally [Sartre] |
| Full Idea: It is possible that those who think that '2 and 2 make 4' is the content of my representations may be forced to resort to a transcendental and subjective principle of unification - in other words, the I. | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], I (A)) | |
| A reaction: He suggests that thoughts themselves unite the mind, externally. If you think of thoughts as internal, you must resort to a transcendental fiction to unify the mind. Personally I think the mind is inherently unified by brain structures. |
| 7106 | The Ego is not formally or materially part of consciousness, but is outside in the world [Sartre] |
| Full Idea: I should like to show here that the Ego is neither formally nor materially in consciousness; it is outside, in the world; it is a being in the world, like the Ego of another. | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], Intro) | |
| A reaction: This idea is the germ of what has got modern externalists about the mind (see quotations from Mark Rowlands) interested in Sartre. Personally I think he is wrong, and the Ego is a part of consciousness. It doesn't, though, have sharp boundaries. |
| 7117 | How could two I's, the reflective and the reflected, communicate with each other? [Sartre] |
| Full Idea: If the 'I' is part of consciousness, there will be two I's: the reflective and the reflected. ...but it is unacceptable for any communication to be established between the reflective I and the reflected I, if they are real elements of consciousness. | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], I (B)) | |
| A reaction: If we accept that there are two orders of consciousness (reflective, about itself, and reflected, about the world) it seems reasonable to say that there cannot be an 'I' in both of them. A nice, and intriguing, argument. |
| 7123 | Knowing yourself requires an exterior viewpoint, which is necessarily false [Sartre] |
| Full Idea: 'To know oneself well' is inevitably to look at oneself from the point of view of someone else, in other words from a point of view that is necessarily false. | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], II (D)) | |
| A reaction: (This is because the Ego cannot be known from the outside). I agree with Russell that the self is most evident when we are engaged with the world, which implies that you can only acquire self-knowledge by studying those engagements. |
| 22225 | My ego is more intimate to me, but not more certain than other egos [Sartre] |
| Full Idea: My I, in efffect, is no more certain for consciousness than the I of other men. It is only more intimate. | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], p.104), quoted by Christine Daigle - Jean-Paul Sartre 2.1 | |
| A reaction: Not sure how to assess this. Other people seem just as real as I do, when I encounter them, as friend or as foe. And in dealing with them we act as if dealing with their Self (rather than their legs, say). So this idea seems a good one. |
| 7116 | When we are unreflective (as when chasing a tram) there is no 'I' [Sartre] |
| Full Idea: There is no 'I' on the unreflected level. When I run after a tram, ...there is no I. There is a consciousness of the tram-needing-to-be-caught, and a non-positional consciousness of consciousness. | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], I (B)) | |
| A reaction: Russell (Idea 5380) says exactly the opposite. My sympathies are more with Russell. I don't just focus on the tram, I focus on the relation between myself and the tram, and that includes my need to catch it, as well as my body. |
| 7124 | The Ego never appears except when we are not looking for it [Sartre] |
| Full Idea: The Ego never appears except when we are not looking for it. | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], II (D)) | |
| A reaction: He denies that we know the Ego when engaged with the world, and agrees with Hume that the ego can't be directly known. All that is left is this, which seems to be introspection 'out of the corner of your eye'. Not persuasive. |
| 7120 | It is theoretically possible that the Ego consists entirely of false memories [Sartre] |
| Full Idea: One cannot rule out the metaphysical hypothesis that my Ego is not composed of elements that have existed in reality (ten years or one second ago), but is merely constituted by false memories. | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], II (D)) | |
| A reaction: (He mentions the evil demon as a source). The problem that false memories (such as George IV 'remembering' he was at Waterloo, when he wasn't) is well known. But this raises the possibility of all memories being false, yet constituting the person. |
| 7110 | If the 'I' is transcendental, it unnecessarily splits consciousness in two [Sartre] |
| Full Idea: The superfluous transcendental 'I' is actually a hindrance. If it existed, it would violently separate consciousness from itself, it would divide it, slicing through consciousness like an opaque blade. | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], I (A)) | |
| A reaction: I see no a priori reason why consciousness should not be split in two, if that's how it is. Personally I am happy with a fairly traditional Cartesian view, that the self is the will and understanding, and the rest of consciousness is its working material. |
| 7115 | Maybe it is the act of reflection that brings 'me' into existence [Sartre] |
| Full Idea: Might it not be precisely the reflective act that brings the me into being in reflected consciousness? | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], I (B)) | |
| A reaction: He admits some sort of self a second-order entity, but this is 'transcendental', and essentially an illusion. This elimination of the first-order self clears the way for the existential view, that we can create whatever self we want. I disagree. |
| 7121 | The Ego only appears to reflection, so it is cut off from the World [Sartre] |
| Full Idea: The Ego is an object that appears only to reflection, and is thereby radically cut off from the World. | |
| From: Jean-Paul Sartre (Transcendence of the Ego [1937], II (D)) | |
| A reaction: This is the culmination of Sartre's attack (in 1937) on the Ego, paving the way for the freedom of existentialism. Personally I don't accept this picture of the Ego as a second-order fiction. My Ego is part of my relationship with the World. |
| 3441 | If a supreme intellect knew all atoms and movements, it could know all of the past and the future [Laplace] |
| Full Idea: An intelligence knowing at an instant the whole universe could know the movement of the largest bodies and atoms in one formula, provided his intellect were powerful enough to subject all data to analysis. Past and future would be present to his eyes. | |
| From: Pierre Simon de Laplace (Philosophical Essay on Probability [1820]), quoted by Mark Thornton - Do we have free will? p.70 |