A Review of Relevant Terminology

empirical—derived from experience.

a posteriori—Latin from ‘what comes after.’ An a posteriori  proposition is one that can be known to be true,
    or false, only by reference to how, as a matter of contingent fact,  things have been, are, or will be.

   --have been, “Alabama was in the Confederacy.”
    --is, “Cal Poly is a university.”
    --will be, “Cal Poly will have new parking structure within five years.”

rational—derived from reason.

a priori—Latin from ‘what comes before.’ An a priori proposition is one that can be known to be true, or
    false without reference to experience, except in so far as experience is necessary in understanding.

      2+2=4
      Bodies are extended in space.
      A triangle has three connected sides.

a posteriori and a priori—a distinction between kinds of  knowledge and how one may acquire its truth.
    You have knowledge that is based upon experience and knowledge  that is not. You have truth that
    is contingent upon experience and truth that is not.

analytic—a  sentence where the concept of the predicate is contained in the subject.

    “All bachelors are unmarried males.”
   This sentence will always be true in virtue of definition and meaning alone. Bachelor=unmarried male

    “All triangles have three connected sides.”
    This sentence will always be true in virtue of definition and meaning alone. triangle=three sided thing

tautology—Frege defined all mathematical truths as those that are  both analytic and tautological.
    Tautologies are generally defined as statements true on all value assignments under
     main logical operator.

    2 = 2, 2 + 2 = 4, If Scott is teaching then Scott is teaching.
    All rectangles have four connected sides.

truth-conditions: statements are either true or false depending upon their conditions which make
    them true or false. For Ayer there are two types of truth conditions:

    empirical—under what conditions of the world is statement ‘x’ true (or potentially true) and under which
    conditions is it false. “Scott is in class.” This can be known by direct observation or by
    appeal to evidence.

    mathematical statements—mathematical statements are tautologies, thus they are always true.

synthetic—a sentence where the concept of the predicate is not contained in the subject.

      “All students have good grades.”
     This sentence can be false or true depending up the the applications of it and the way the world is.

      “Rocks are heavy.”
      This sentence can be false or true depending upon the rocks are being referenced.

metaphysics—Ayer is seeking to redefine ‘metaphysics’ in terms of significant statements in
    language—empirically verifiable (in principle) statements and tautologies.

principle of verification—a sentence’s meaning is determined by its method of verification.
    If you don’t know how to verify a statement, there is a good chance it does not have any
    meaning.

    Ayer states, “We need only to formulate the criterion which enables us to test whether a sentence
    expresses a genuine proposition about a matter of fact, and then point out that the sentences under
    construction fail to satisfy it.”(35)

    For example, from Hegel’s Philosophy of Right, p. 45

   “Since matter in itself does not belong to itself.”

   What does this statement mean? How would you go  about verifying or try to find the truth-conditions,
    i.e., what makes this statement true or false?

   Another example, from Hegel’s Philosophy of Right, p. 30

 “It is the will whose potentialities have become fully explicit which is truly infinite, because its object
    is itself, and so is not in its eyes an ‘other’ or a barrier; on the contrary, in its object this will has
    simply turned its back on itself.”

 So, the thinking philosopher trying to give a shot at understanding this passage will require making
    sense of the word ‘will’. Hegel defines the ‘will’ as:

 “The will contains the element of pure indeterminacy or that pure reflection of the ego into itself
    which involves the dissipation of every restriction and every content either immediately presented
    by nature, by needs, desires, and  impulses, or given and determined by any means whatever.
   This is the unrestricted infinity of absolute abstraction or  universality, the pure thought of oneself.”

  My question is then, how would we even attempt to verify or ascertain the truth conditions of this
    statement? Specifically, how would we attempt to verify that the will  contains the element of pure
    indeterminacy and that this is the same thing as the pure reflection of the ego into itself involving
    dissipation?

 Ayer would claim statements like these are grammatically correct yet they have no meaning. The
    appearance of the statement as meaningful is misleading because although it satisfies our rules
    of grammar, it is not verifiable, thus it has no meaning—and we should discard it.

 He states, (1) “The criterion we use to test the genuineness of apparent statements of fact is the
    criterion of verifiability. We say that a sentence is factually significant to any given person, if and
    only if, he knows how to verify the proposition which it purports to express—that is, if he knows
    what observations would lead him, under certain conditions, to accept the proposition as being true,
    or reject it as being false. (2) If, on the other hand, the putative proposition is of such a character
    that the assumption of its truth, or falsehood, is consistent with any assumption whatsoever
    concerning the nature of his human experience, then, as far as he is concerned, it is, if not a
    tautology, a mere-pseudo proposition. The sentence expressing it may be emotionally significant
    to him; but it is not literally significant. (3) We enquire in every case what observations would lead
    us to answer the question, one way or the other; and, if none can be discovered, we must conclude
    that the sentence under consideration does not, as far as we are concerned, express a genuine
    question, however strongly its grammatical appearance does.” (35)

There are three parts to this criterion.

(1) A statement is a fact if and only if someone knows under what conditions the statement is true or false.

(2) Notice the qualifier here of ‘future experience.’ Ayer’s point is that we have no assurance of future events
    being like past ones, and that we can’t use past experiences to justify the same type of experiential
    regularity in the future.

 For example, you assert, “I will graduate next year.” For Ayer this is not an empirically verifiable proposition,
    thus it is a pseudo-proposition. However, more importantly, notice he says, “..it may be emotionally
    significant to him; but it is not literally significant.” Statements like these assert your feelings about
    the future, however your feelings are not empirically verifiable, thus statements with expressions like
    these are not factually significant. Ayer’s emotive theory of ethics is the  result of his view of language,
    and (2).

(3) The role of procedure.  What observation or set of observations would lead us to answer the question
    that the statement is factually significant. If none (obs.) can be found, then the statement may look
    significant, but it is not.

Two-types of verifiability: practical and in principle.

Practical—statements which can be verified with enough work.
 “Kilaminjaro is 12,345 feet.”
 “San Diego is 123.4 miles from Riverside.”
 “Cal Poly is a school in California.”
 “There are 4 billion pennies in existence.”
 “Judy Miles is Chair of the Philosophy Department.”
 “Cellular phones cause brain cancer.”

In Principle—statements that are factually significant, but where, for any number of reasons,
    practical observations cannot be made.

 “There is a big lake on the planet Mars.”

To verify this statement, we have to know what a ‘lake’ is,  what ‘Mars’ is and what would count
    as a ‘lake on Mars.’  We can in principle do this if we had the means to get to Mars.

 “There is a big lake on planet Twin Earth.”

To verify this statement, we have to know what a ‘lake’ is, what ‘Twin Earth’ is and what would count
as a ‘lake on Twin Earth.’ We cannot in principle do this because ‘Twin Earth is not an empirical object
such that it is available for in principle verification. The grammar misleads us in this case, where as
it didn’t in the former.

Other statements that are in principle verifiable.
“The temperature of the Earth’s core.”
We know that to measure the temperature, we would need some type of measuring device and a
    way to get it there.

“Evolution adequately accounts for the fossil record.”
We know what would count as representative examples of the correct chain of evidence in the fossil record.

Two further qualifications of ‘verifiable.’ Ayer distinguishes two senses of the word, strong and weak.
  strong—a statement is strongly verifiable, if and only if, its truth can be conclusively established in experience.
  weak—a statement is weakly verifiable, if and only if, itspossible for experience to render it probable.

Ayer rejects strong verifiability because it leads to the very kind of statements that he is seeking
    to reject. Consider the statement,

 “All women are mortal.”

To use the criterion of strong verifiability, we would have to examine every single woman in history,
    however we know this is impossible. What Ayer points out is that statements like these assume
    a law like characteristic, allowing one to make claims about the future based upon the past.

   However, we already know that statements about the future, are at best, expressions of emotions or
    attitudes, and not expressions of fact. So strong verifiability ends up undermining itself.

Weak verifiability simply asks, “Would any observations be relevant to the determination of its truth
    or falsehood?” If the answer to this question is ‘no’, then we can conclude that the statement is
    nonsensical.(38)

The Technical Definition of Weak Verifiability

“Let us call a proposition which records an actual or possible observation an experiential proposition.
    Then we may say that it is the mark of a genuine factual proposition, not that it should be equivalent
    to an experiential proposition, or any finite number of experiential propositions, but simply that some
    experiential propositions can be deduced from it in conjunction with certain other premises without
    being deducible from those other premises alone.” (39)

Goya example
1. A painting with a particular form and style.
2. Records may indicate a picture.
3. There is a lack of evidence of forgery.
4. Goya had the same style as (1).
------
C—Goya painted the picture.

What is important to notice is that we can more or less all agree upon how 1-4 stand as standards of
    evidence, that is, we would know what would count for or against 1-4.  To put this in the form of weak
    verifiability then would entail:

Genuine Factual Proposition—Goya painted the picture.
Experiential Propositions— a proposition that records an actual or possible observation, i.e., 1-4

Some Experiential Propositions can be deduced from a Genuine Factual Proposition in conjunction with
    other premises, but it (GFP) is not deducible from those other premises alone.
 

2. Records may indicate a picture.
3. There is a lack of evidence of forgery.
------
C—Goya painted the picture.

*C here is not simply deducible from 2 and 3, we also need 1 and 4. Premises 1 and 4 give the experiential
    content necessary to make ‘Goya painted the picture’ the conclusion.

**Likewise, we can deduce 1 and 4 from C by reference to artistic style which can be an object of actual
    observation.

Thus, * and ** show “Goya painted the picture” to be a genuine factual proposition because it is not
    deducible from other premises alone which is * and ** satisfies EP’s being deducible from GFP’s.
    It meets the criterion of weak verifiability.

Ayer’s goal is make philosophy a genuine branch of knowledge distinct from metaphysics—or at least the
    kind of metaphysics he finds objectionable. “Metaphysics” for Ayer is a pejorative term, it is bad for
    something to be metaphysical.

Ayer defines a metaphysical sentence as one that, “purports to express a genuine proposition, but does,
    in fact, express neither a tautology nor an empirical hypothesis. And as tautologies and empirical
    hypotheses form the entire class of significant propositions, we are justified in concluding that all
    metaphysical assertions are non-sensical.

Ayer goes on to give examples in the history of philosophy where there are metaphysical sentences.

Substance/Essence—That which makes something ‘x’ versus ‘y’.
   Humans have an essence that they share. This use of ‘essence’ indicates that we all have ‘x’ and
    without ‘x’  we would fail to be humans.

 Ayer’s objection: Humans have sensible properties, e.g., skin color, eye color, height, sex, etc…
    As a feature of our  language, we use words to indicate these properties, however, they also
    indicate a thing-itself (an essence). The thing-itself must be recognized as a false reference, and
    it leads one into metaphysical illusion—there are essences. The word human refers to a set of
    properties that are observable. Ayer will refer to these properties that are observable in experience
    as ‘sense data.’

So we might conclude with the following, Ayer states, “As to the validity of the verification principle,
in the form which we have stated it, a demonstration will be given in the course of this book. For it will
be shown that all propositions, which have factual content, are empirical hypotheses; and that the
function of a rule is to provide a rule for the anticipation of experience. And this means that every
empirical hypothesis must be relevant to some actual, or possible experience, so that a statement
which is not relevant to any experience is not an empirical hypothesis, and accordingly has no factual
content. But this is precisely what the principle of verifiability asserts.” (41)

Summary: Ayer is attacking traditional metaphysics where language goes beyond its simplistic function.
He believes there are two classes of significant statements: empirically verifiable ones, and tautologies.
If a sentence is not one of these two classes, it is a metaphysical sentence and should be done away
with. He supports both practical verifiability and in principle verifiability. Finally, his chosen version of a
criterion of verifiability is weak verifiability because it doesn’t suffer the problems of strong or conclusive
verifiability.