Lecture 4  The Paleolithic period (or Old Stone Age) is the earliest period of human development. Dating from about 2 million years ago, and ending in various places between 50,000 and 10,000 years ago, it is roughly co-extensive with the geologic period known as the Pleistocene, an epoch which was marked by continuous cooling, which resulted in several ice ages. During the period, hominids become increasingly advanced in terms of fire and tool making, and modern humans emerge.

Lecture 4  Evidence of Cro-Magnon humans (one of several varieties of modern humans that lived during the period) indicates they lived some 50,000-10,000 years ago. Anatomically the same as today’s Homo sapiens and fossil remains, graves, artifacts, and dwellings have been found throughout Europe.  It is believed that their arrival in Europe, when they encountered another hominid species, the Neanderthals, resulted in the extinction of the latter.  In a recent article in “The Science Times,” a regular feature of The New York Times’ Tuesday addition, it was hypothesized that Cro-Magnons were so startled to be confronted with another bi-pedal, tool using (and much larger!) hominid, that they developed the practice of designing beads that would identify them.

Lecture 4  Which of the following examples that scientists cited in the film as evidence of the existence of modern humans at particular sites did you find convincing? Unconvincing (a stretch)? Or you’re unsure? Consider both the physical evidence and the reasoning from it to a hypothesis about the birth of the human mind, human creativity, and/or human expression?

 The discovery of what scientists call “beads”  The differences in the treatment that humans and Neanderthals provided the dead?  Cave paintings?  Fossil evidence (particularly skulls) of Neanderthals and humans?  Real and relatively quick innovations (in, for example, spears and spear heads)?  Migrations of early humans across Europe?  Cave instruments and music?  Biological changes in the brain?  Comparison of humans and chimpanzees?  The emergence and significance of language?  Cultural forces overriding biological forces?

Demarcation: Ayer and “verifiabiliity”  Although Ayer doesn’t single out science (his immediate target is a form of metaphysics), his criterion of “verifiability” was adopted for a time by scientists and philosophers of science as a criterion of demarcation between science and “pseudo-science” (and “non-science” – e.g., the arts)  A statement (hypothesis or theory) is genuinely meaningful (genuinely scientific) only if it is able to be verified by experience.  His immediate goal: to show that statements (hypotheses or theories) that are not verifiable are “nonsense” (pseudo-scientific).

Demarcation: Ayer and “verifiabiliity”  As claims about a so-called transcendental reality are, in principle, not empirical (based on sensory experience), why not just go after the kinds of argument that are supposed to support them?  For one thing, one might be willing to say that one’s statements are not based on sensory experience … but are rather the product of the cognitive capacity of “intuition”  So they refuse to accept the grounds of the objection.

Demarcation: Ayer and “verifiabiliity”  For another, one cannot demonstrate that an argument is invalid by demonstrating that its conclusion is false.  Remember that validity does not rule out false premises or false conclusions, only arguments in which it is possible for the premises to be true and the conclusion false.  Valid arguments can have true premises and a true conclusion; false premises (one or more) and a false conclusion; false premises (one or more) and a true conclusion.

Demarcation: Ayer and “verifiabiliity”  A valid argument  All men are green.  Socrates is a man  Socrates is green.  An invalid argument  All men are mortal.  Socrates is mortal  Socrates is a man.

Demarcation: Ayer and “verifiabiliity”  So the most useful way to demonstrate that some statement (or hypothesis or theory) is not meaningful (cognitively significant) or is nonsense is to show that it cannot be verified by any sensory experiences.  Verifiable: a statement is verifiable only if we can identify what observations would show a sentence to be true.  Instead of arguing for or against the nature of the mind, focus on “the literal significance of language”  Metaphysicians fail to produce sentences which conform to the conditions under which alone a sentence can be “literally significant.”

Demarcation: Ayer and “verifiabiliity”  Part of Ayer’s argument:  Distinguish between “propositions” and “sentences”  Propositions are what sentences express  For example, sentences of different languages might express the same proposition (e.g., “It is currently raining here”)  Demonstrate that some kinds of sentence do not express a genuine proposition about “a matter of fact”.

Demarcation: Ayer and “verifiabiliity”  Part of Ayer’s argument:  Distinguish between “practical verifiability” and “verifiability in principle”  An example: “There are mountains on the dark side of the Moon.”  Another: “There is little red schoolhouse on the far side of the Moon.”  Although neither is practically verifiable, both are verifiable in principle.  His criterion of “verifiability” appeals to “verifiable in principle”

Demarcation: Ayer and “verifiabiliity”  Part of Ayer’s argument:  A distinction between a “strong” and “weak” sense of “verifiable”  The strong sense: show that a sentence is such that (it or the proposition it expresses) can be shown to be true.  The weak sense: show that a sentence is such that (it or the proposition it expresses) can be shown to be probable.  Some argue for the former, but that would rule out things like “laws of nature”.  Accordingly, he opts for the weak sense.