A Priori and A Posteriori

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Reply Wed 6 Dec, 2006 11:07 am
No discussion really (unless you have something to say), just learning and taking notes.

A Priori and A Posteriori

The terms "a priori" and "a posteriori" refer primarily to how or on what basis a proposition might be known. A proposition is knowable a priori if it is knowable independently of experience. A proposition is knowable a posteriori if it is knowable on the basis of experience. The a priori/a posteriori distinction is epistemological and should not be confused with the metaphysical distinction between the necessary and the contingent or the semantical or logical distinction between the analytic and the synthetic. Two aspects of the a priori/a posteriori distinction require clarification: the conception of experience on which the distinction turns; and the sense in which a priori knowledge is independent of such experience. The latter gives rise to important questions regarding the positive basis of a priori knowledge.

A Priori and A Posteriori [Internet Encyclopedia of Philosophy]

The second distinction is between necessary and contingent truths. A necessary truth is one that could not have been false, one that would have been true no matter how things had turned out. As Leibniz put it, a necessary truth is one that is "true in all possible worlds." Plausible examples include "17 is prime," "If Moore is a bachelor, he is unmarried," and so on.
The third distinction is between truths knowable a priori and those knowable only a posteriori. An a priori truth is one that is knowable independently of experience, or without empirical evidence. Plausible examples include "9 = 32," "Either Gilbert Ryle was a plumber or he wasn't," and the like. A truth is knowable only a posteriori ("on the basis of experience") just in case it is knowable but not knowable a priori: "The number of planets is nine" or "Gilbert Ryle was a bachelor," for instance.
Given the explanations sketched above, one might fairly suspect that the three pairs of distinctions coincide. That is: perhaps a truth is analytic if and only if it is necessary, and if and only if it is knowable a priori. And, in much of twentieth century analytic philosophy, either the equivalence of these distinctions was taken for granted or-worse-the distinctions were simply conflated.3 As Soames nicely brings out, a number of arguments from the period smuggle in the equivalence as a tacit premise. The essential point for the evolution of 20th-century philosophy is that once the equivalence is accepted, an extremely humble conception of philosophy itself is only a few steps away. Here is one route to this humble conception. First, philosophical claims themselves are often taken to be both necessary and a priori: according to many philosophers, the business of philosophy is to deliver truths that describe what the world must be like and that are knowable by reason alone. Second, since analytic truths are "true in virtue of meaning," and since what a word means is a conventional matter, it is natural to think that analytic truths are somehow "true by convention"-that the basis of their truth lies in our decisions or intentions concerning the use of words, rather than in the (extra-linguistic) world. As Ayer put it, analytic truths are true "simply because we never allow them to be anything else." But now, if we assume the equivalence, then necessary and a priori truths are also true by convention, in which case they are not about the world either. And since the truths of philosophy are supposed to be necessary and a priori, this means that philosophy, contrary to the traditional advertisement, is not about the world, let alone the Ultimate Nature of Reality. "The propositions of philosophy are not factual," Ayer announced, "but linguistic in character . . . they express definitions, or the formal consequences of definitions." Philosophy is turned into the analysis of language: thus the title of Rudolf Carnap's classic 1932 paper, "The Elimination of Metaphysics through Logical Analysis of Language."

Alex Byrne and Ned Hall: Necessary Truths
Electra phil
Reply Wed 6 Dec, 2006 11:37 am
@Electra phil,
What Philosophy Is and How to Study It

An excerpt from Chapter 1 of Objectivism: The Philosophy of Ayn Rand

Philosophy is not a bauble of the intellect, but a power from which no man can abstain. Anyone can say that he dispenses with a view of reality, knowledge, the good, but no one can implement this credo. The reason is that man, by his nature as a conceptual being, cannot function at all without some form of philosophy to serve as his guide.

Ayn Rand discusses the role of philosophy in her West Point lecture "Philosophy: Who Needs It." Without abstract ideas, she says,
[INDENT]you would not be able to deal with concrete, particular, real-life problems. You would be in the position of a newborn infant, to whom every object is a unique, unprecedented phenomenon. The difference between his mental state and yours lies in the number of conceptual integrations your mind has performed. You have no choice about the necessity to integrate your observations, your experiences, your knowledge into abstract ideas, i.e., into principles. 1
Your only choice, she continues, is whether your principles are true or false, rational or irrational, consistent or contradictory. The only way to know which they are is to integrate your principles.
[INDENT]What integrates them? Philosophy. A philosophic system is an integrated view of existence. As a human being, you have no choice about the fact that you need a philosophy. Your only choice is whether you define your philosophy by a conscious, rational, disciplined process of thought and scrupulously logical deliberation - or let your subconscious accumulate a junk heap of unwarranted conclusions, false generalizations, undefined contradictions, undigested slogans, unidentified wishes, doubts and fears, thrown together by chance, but integrated by your subconscious into a kind of mongrel philosophy and fused into a single, solid weight: self-doubt, like a ball and chain in the place where your mind's wings should have grown. 2
Philosophy, in Ayn Rand's view, is the fundamental force shaping every man and culture. It is the science that guides men's conceptual faculty, and thus every field of endeavor that counts on this faculty. The deepest issues of philosophy are the deepest root of men's thought (see chapter 4), their action (see chapter 12), their history (see the Epilogue) - and, therefore, of their triumphs, their disasters, their future.

Philosophy is a human need as real as the need of food. It is a need of the mind, without which man cannot obtain his food or anything else his life requires.

To satisfy this need, one must recognize that philosophy is a system of ideas. By its nature as an integrating science, it cannot be a grab bag of isolated issues. All philosophic questions are interrelated. One may not, therefore, raise any such questions at random, without the requisite context. If one tries the random approach, then questions (which one has no means of answering) simply proliferate in all directions.

Suppose, for example, that you read an article by Ayn Rand and glean from it only one general idea, with which, you decide, you agree: man should be selfish. How, you must soon ask, is this generality to be applied to concrete situations? What is selfishness? Does it mean doing whatever you feel like doing? What if your feelings are irrational? But who is to say what's rational or irrational? And who is Ayn Rand to say what a man should do, anyway? Maybe what's true for her isn't true for you, or what's true in theory isn't true in practice. What is truth? Can it vary from one person or realm to another? And, come to think of it, aren't we all bound together? Can anyone ever really achieve private goals in this world? If not, there's no point in being selfish. What kind of world is it? And if people followed Ayn Rand, wouldn't that lead to monopolies or cutthroat competition, as the socialists say? And how does anyone know the answers to all these (and many similar) questions? What method of knowledge should a man use? And how does one know that?

For a philosophic idea to function properly as a guide, one must know the full system to which it belongs. An idea plucked from the middle is of no value, cannot be validated, and will not work. One must know the idea's relationship to all the other ideas that give it context, definition, application, proof. One must know all this not as a theoretical end in itself, but for practical purposes; one must know it to be able to rely on an idea, to make rational use of it, and, ultimately, to live.
*** [/CENTER]
In order to approach philosophy systematically, one must begin with its basic branches. Philosophy, according to Objectivism, consists of five branches. The two basic ones are metaphysics and epistemology. Metaphysics is the branch of philosophy that studies the nature of the universe as a whole. (The Objectivist metaphysics is covered in the present chapter on "Reality.") Epistemology is the branch that studies the nature and means of human knowledge (chapters 2-5). These two branches make possible a view of the nature of man (chapter 6).

Flowing from the above are the three evaluative branches of philosophy. Ethics, the broadest of these, provides a code of values to guide human choices and actions (chapters 7-9). Politics studies the nature of a social system and defines the proper functions of government (chapters 10 and 11). Esthetics studies the nature of art and defines the standards by which an art work should be judged (chapter 12).

In presenting Objectivism, I shall cover the five branches in essential terms, developing each in hierarchical order, and offering the validation of each principle or theory when I first explain it.

The True, said Hegel, is the Whole. At the end of our discussion, to borrow these terms, you will see a unique Whole, the Whole which is Ayn Rand's philosophic achievement. You may then judge for yourself whether it is an important achievement - and whether it is True.


(1) Ayn Rand, Philosophy: Who Needs It (New York: Bobbs-Merrill, 1982) New York: Signet, 1984. p. 5. [back]

(2) Ibid. [back]

What Philosophy Is, and How to Study It | An Excerpt from Objectivism: The Philosophy of Ayn Rand by Leonard Peikoff

Hey I took a completely INTUITIVE "shot in the dark" according to this article and on target! If anyone cares, that is. lol :p


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