De nouvelles observations de Hubble montrent que ce n’est pas à quoi s’attendaient les chercheurs et que cela pourrait avoir des implications pour définir exactement ce qu’est vraiment lamatière noire
Le Ili pika (Ochotona iliensis), est un petit lapin anthropophage avec des oreilles de souris et il a été photographié en Chine pour la première fois en deux décennies.
Le mammifère, qui vagabonde dans les monts Tianshan, en...
The Stoics recognized the importance of both the Liar and the Sorites paradoxes (Cicero Acad. 2.95–8, Plut. Comm.Not. 1059D–E, Chrys. Log. Zet. col.IX). Chrysippus may have tried to solve the Liar as follows: there is an ineliminable ambiguity in the Liar sentence (‘I am speaking falsely’, uttered in isolation) between the assertibles (i) ‘I falsely say I speak falsely’ and (ii) ‘Iam speaking falsely’ (i.e. I am doing what I'm saying, viz. speaking falsely), of which, at any time the Liar sentence is uttered, precisely...
Arguments are—normally—compounds of assertibles. They are defined as a system of at least two premises and a conclusion (D. L. 7.45). Syntactically, every premise but the first is introduced by ‘now’ or ‘but’, and the conclusion by ‘therefore’. An argument is valid if the (Chrysippean) conditional formed with the conjunction of its premises as antecedent and its conclusion as consequent is correct (S. E. PH 2.137; D. L. 7.77). An argument is ‘sound’ (literally: ‘true’), when in addition to being valid it has true premises. The Stoics defined...
The founder of the Stoa, Zeno of Citium (335–263 BCE), studied with Diodorus. His successor Cleanthes (331–232) tried to solve the Master Argument by denying that every past truth is necessary and wrote books—now lost—on paradoxes, dialectics, argument modes and predicates. Both philosophers considered knowledge of logic as a virtue and held it in high esteem, but they seem not to have been creative logicians. By contrast, Cleanthes' successor Chrysippus of Soli (c. 280–207) is without doubt the second great logician in the history of logic. It...
Theophrastus is further credited with the invention of a system of the later so-called ‘wholly hypothetical syllogisms’ (Theophrastus fr. 113 Fortenbaugh). These syllogisms were originally abbreviated term-logical arguments of the kind
اقتباس :
If [something is] A, [it is] B. If [something is] B, [it is] C. Therefore, if [something is] A, [it is] C.
Aristotle is also the originator of modal logic. In addition to quality (as affirmation or negation) and quantity (as singular, universal, particular, or indefinite), he takes categorical sentences to have a mode; this consists of the fact that the predicate is said to hold of the subject either actually or necessarily or possibly or contingently or impossibly. The latter four are expressed by modal operators that modify the predicate, e.g. ‘It is possible for A to hold of some B’; ‘Anecessarily holds of every B’.
Aristotle's non-modal syllogistic (Prior Analytics A 1–7) is the pinnacle of his logic. Aristotle defines a syllogism as ‘an argument (logos) in which, certain things having been laid down, something different from what has been laid down follows of necessity because these things are so’. This definition appears to require (i) that a syllogism consists of at least two premises and a conclusion, (ii) that the conclusion follows of necessity from the premises (so that all syllogisms are valid arguments), and (iii) that the conclusion...
Argu[size=17]Pre-Aristotelian evidence for reflection on argument forms and valid inference are harder to come by. Both Zeno of Elea (born c. 490 BCE) and Socrates (470–399) were famous for the ways in which they refuted an opponent's view. Their methods display similarities withreductio ad absurdum, but neither of them seems to have theorized about their logical procedures. Zeno produced arguments...
Logic as a discipline starts with the transition from the more or less unreflective use of logical methods and argument patterns to the reflection on and inquiry into these methods and patterns and their elements, including the syntax and semantics of sentences. In Greek and Roman antiquity, discussions of some elements of logic and a focus on methods of inference can be traced back to the late 5[size=12]th century BCE. The Sophists, and later Plato (early 4th c.) displayed an interest...
Consider the veridical experiences involved in cases of perception; cases where one genuinely sees or otherwise perceives an object for what it is. Like sense-datum theorists, and unlike intentionalists, naive realists hold that such experiences themselves consist of relations of awareness to objects. However, like intentionalists, naive realists reject sense-data and appeal instead to ordinary objects. So the naive realist holds,...
3.3.1 The Intentionalist Theory and the Problem of Perception
At Level 1, the intentional theory of experience treats perceptual experience as a form of intentionality conceived of as a form of mental representation (hence it is also sometimes called the representationalist theory of experience). “Intentionality” is a term with its origins in scholastic philosophy (see Crane 1998b), but its current use derives from Brentano (1874), who introduced the term “intentional...
3.2.1 The Adverbial Theory and the Problem of Perception
Some philosophers agree with the Phenomenal Principle that whenever a sensory quality appears to be instantiated then it is instantiated, but deny that this entails the existence of sense-data. Rather, they hold that we should think of these qualities as modifications of the experience itself (Level 1). Hence when someone has an experience of something brown, something like brownness is instantiated, but in the experience itself, not an object. This is not to say that the experience is brown,...
In this section we will consider the leading theories of experience of the last hundred years. These theories are understood here as responses to the Problem of Perception. (There are a number of theories of perception which are not discussed in this entry, either because they are not responses to this specific problem (like the causal theory of Grice (1961) and Lewis (1988), and Burge (2010)) or because they require an entire entry of their own (like the phenomenology of Husserl (1900–1) and Merleau-Ponty (1945); see the entry on
A hallucination is an experience which seems exactly like a veridical perception of an ordinary object but where there is no such object there to be perceived. Like illusions, hallucinations in this sense do not necessarily involve deception. And nor need they be like the real hallucinations suffered by the mentally ill, drug-users or alcoholics. They are rather supposed to be merely possible events: experiences which are indistinguishable for the subject from a genuine perception of an object. For example, suppose one is now having a veridical...
The Problem of Perception is that if illusions and hallucinations are possible, then perception, as we ordinarily understand it, is impossible. The Problem is animated by two central arguments: the argument from illusion (§2.1) and the argument from hallucination (§2.2). (A similar...
Sense-perception has long been a preoccupation of philosophers. One pervasive and traditional problem, sometimes called “the Problem of Perception”, is created by the phenomena of perceptual illusion and hallucination: if these kinds of error are possible, how can perception be what we ordinarily understand it to be, an openness to and awareness of the world? The present entry is about how these possibilities of error challenge the intelligibility of the phenomenon of perception, and how the major theories of experience in the last century are...
Let us now see how Kelsen thought that the basic norm helps to explain the sense in which law is a normative domain and what this normativity consists in. The first and crucial point to realize is that for Kelsen the idea of normativity is tantamount to a genuine “ought”, as it were; it is a justified demand on practical deliberation. A certain content is regarded as normative by an agent if and only if the agent regards that content as a valid reason for action. As Joseph Raz noticed, Kelsen agrees with the Natural Law tradition in this particular...
Common wisdom has it that Kelsen’s argument for the presupposition of the basic norm takes the form of a Kantian transcendental argument. The structure is as follows: [list="margin-top: 0.5em; color: rgb(26, 26, 26); font-family: serif; font-size: 16.5px; line-height: 21px; background-color: rgb(255, 255, 255);"] [*]P is possible only if Q
The idea of a Pure Theory of Law was propounded by the formidable Austrian jurist and philosopher Hans Kelsen (1881–1973) (see the bibliographical note). Kelsen began his long career as a legal theorist at the beginning of the 20th century. The traditional legal philosophies at the time, were, Kelsen claimed, hopelessly contaminated with political ideology and moralizing on the one hand, or with attempts to reduce the law to natural or social sciences, on the other hand. He found both of these reductionist endeavors seriously flawed. Instead, Kelsen...
The kind of levels involved in evolutionary epistemology are quite different than the kind of levels of selection which are discussed much more often in the “levels of selection” debate in evolutionary biology. In evolutionary biology, the “levels” of selection under discussion are levels of scale. The debate concerns whether genes are always the “units” or “targets” of selection, or whether selection can occur on higher levels, like organisms, groups, and species. The levels involved in evolutionary epistemology, on the other hand, are levels...
Population dynamics, sometimes referred to as “replicator dynamics”, offers a tractable way to model the evolution of populations over time under the kinds of selective pressures that can be characterized by static optimization models. This is often necessary, since the dynamics of such populations are often difficult to predict purely on the basis of static considerations of payoff differences. The so-called “replicator dynamics” were named by Taylor and Jonker (1978) and generalized by Schuster and Sigmund (1983) and Hofbauer and Sigmund (1988)....
Although Campbell and Popper both pointed to the continuity between the evolution of human knowledge and the evolution of knowledge in non-human organisms, much of the early work in evolutionary epistemology focused on the human condition. However, recent empirical investigations by psychologists, cognitive ethologists, cognitive neuroscientists and animal behaviorists have revealed that animals, both primates and non-primates, have much more sophisticated cognitive capacities than were previously suspected (Panksepp 1998, Heyes and Huber 2000,...
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