Philosophy 125:  Study Questions 
G. Randolph Mayes

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Answer to Sample Question

Question:  In what way, if any, does the representational theory of perception bear on our understanding of the nature of truth?

According to the representational theory of perception our sense organs provide us with internal images or representations of the external world.  So, for example, if Sara is looking at a llama she will, as a result,  have a visual image of the llama which is distinct from llama itself.  If Sara is not looking at a llama she will ordinarily have no such visual image despite the fact that a llama is present, and if Sara is hallucinating a llama, then she will have a visual image of a llama despite there being no llama present. 

One important implication of the representational theory of perception is that we have no direct way of checking to see whether our representations are correct. This is because Sara has no ability to compare her representation of a llama with the llama itself.  The llama as it exists beyond perception is not accessible to Sara.  Sara can only compare her representations to each other.  So, for example, if Sara  is wondering whether she is hallucinating a llama she can pinch herself or ask her friend Martin if he sees the llama, but this will only allow her to compare her representations to see whether they contradict or support each other.

There are two major theories of truth: the correspondence theory and the coherence theory.  According to correspondence theory,  a statement is true if it corresponds to the facts.  So, for example, "There is a llama in Sara's garage" is true if and only if there is, in fact, a llama in Sara's garage.  This is commonsensical, and it makes truth entirely objective.  Sara may believe that there is a llama in her garage, or she may disbelieve it, or she may have no beliefs concerning llamas in her garage at all.   The important point  is that whether or not there is a llama in her garage has nothing to do with what Sara believes, but only with what is actually the case.

Interestingly, because Sara has no direct cognitive access to what is actually the case, she can never know for sure whether there is a llama in her garage.  No matter how carefully she examines the situation, it remains possible that she is mistaken.  Hence, taken together, the representational theory of perception and the correspondence theory of truth imply that we can never be certain that the external world is as it appears. 

According to the coherence theory, a statement is true if it "fits" or is supported by the rest of a person's beliefs.   According to the coherence theory, Sara's belief that there is a llama in her garage is true if it fits with her memory of ordering a llama, taking delivery in in that morning, seeing it in the garage, believing that Martin sees it too, etc.  Taken together, the representational theory of perception and the coherence theory of truth seem to allow more direct cognitive access to the truth, since the truth is just a relation between our representations.  

The coherence theory, however, does not preserve the objectivity of truth.   Sara's belief that there is a llama in the garage may cohere perfectly with all of her other beliefs, whereas Martin's belief that there is not a llama in the garage may cohere perfectly with all of his.  The coherence theory of truth would imply that both Sara's and Martin's beliefs are true, even though they contradict each other. 

Question 1

Are there any beliefs of which we can be absolutely certain?  What does your answer to this question imply about the nature of scientific knowledge?

One can mean different things by the phrase "absolutely certain."   If the statement "I am absolutely certain that X" is understood to be a report about how confident one feels about the truth of X, then absolute certainty can be attained by faith or ignorance of contrary evidence.  In philosophical contexts, however, the statement is ordinarily interpreted to mean that the truth of X is absolutely guaranteed, and beyond all rational doubt.  Understood in this sense, the answer to the question is no.

In Chapter 2, DeWitt discusses the Cartesian project of finding a bedrock of certainty upon which to build all of our knowledge about the world.  Descartes attempted to show that we could at least be guaranteed of our own existence, since even to doubt ones existence one must exist.  The argument is interesting, but it does not establish its conclusion with certainty, and few philosophers accept the argument today.  The real problem is that even if ones own existence is certain, nothing much else seems to follow from that; i.e., it does not serve as a foundation for scientific knowledge.

Modern science began to emerge in the 17th century largely as a result of advances in experimental method.  Experiments are based on observations, which are themselves based in perception.  Since, as Descartes argued, perception is inherently fallible, it follows that no results based on experiments are certain.  Certainty, however, is not required in science.  All that is required is a method that makes it more reasonable to believe one thing than another, and science succeeded in providing this.

Question 2  (Student Sample)

How does the jigsaw metaphor employed in Chapter 1 relate to the discussion of theories of truth in Chapter 2?

In Chapter 1, DeWitt compares a jigsaw puzzle to a worldview, in which all beliefs, or puzzle pieces, fit together to form an interlocking, consistent belief system.  While peripheral beliefs may be changed without altering one's entire belief system, a belief that is at the core of the belief system cannot be removed without disrupting and replacing the other beliefs that "lock" around it. 

For example, if I believe that the Earth is around 6,000 years old, as stated in the Bible, I cannot also believe that dinosaurs roamed the Earth a hundred million years ago.  If I want to adopt the belief that dinosaurs existed at that time, I must first compromise my core belief that the Earth is 6,000 years old and replace it with the belief that the Earth is older than is stated in the Bible.

According to the coherence theory of truth, as discussed in Chapter 2, what makes a belief true is how it ties in with other beliefs in one's worldview.  This ties into the jigsaw metaphor used in Chapter 1 because even a belief that doesn't correspond with reality may still be considered true if the other "puzzle pieces" still fit around the core belief. 

For example, the belief that the Earth is 6,000 years old is false according to the correspondence theory of truth because it does not correspond with objective reality.  However, according to the coherence theory, if I hold onto this belief, it is true as long as my other beliefs all cohere to it.  If I choose to deny the existence of dinosaurs, for instance, this is a true belief consistent with my worldview because I don't believe the Earth existed in the time dinosaurs supposedly lived here.  The puzzle pieces still fit together, even if my worldview is not consistent with objective reality. If I decide to believe that dinosaurs lived a hundred million years ago, my belief about the age of the Earth becomes false because the puzzle pieces cease to fit together.

Question 3  (Student Sample)

Clarify the distinction between an empirical fact and a conceptual fact.  Identify an empirical fact.  Then identify a conceptual fact by using some of the concepts employed in the proposition that expresses the empirical fact.  (Don't use any of the examples in the book or lecture.)

An empirical fact is a fact that is based on experience.  The most direct kind of experience is one that I can personally experience through one of my five senses.  A conceptual fact is a belief that comes from my worldview and the definitions that I accept for things.  My worldview beliefs are based on what I accept as a valid definition of some category of thing or interconnected things. 

An example of an empirical fact is that my cat sitting in my lap.  I can see my cat.  I cat hear my cat purring.  I can feel my cat as I pet her.  I can smell her fishy cat breath if I nuzzle my head against hers.  I could even taste her fur if I really wanted to.  All of these observations are coming from one of my senses. 

A conceptual fact that supports my observation of my cat sitting in my lap is that the cat in my lap is the same cat that sat in my lap this morning before I left for work.  That I strongly believe that my cat has not left the house, crossed the neighborhood, and traded residences with another cat that resembles my cat while I was gone is a conceptual fact I hold about what kind of creatures cats are.  I believe that cats cannot open locked doors.  I also believe my cat stayed inside my house the entire time I was gone because I  strongly believe that cats cannot walk through walls because my worldview does not allow for objects as large and dense as cats to pass through other dense objects such as walls.

(Note from instructor:  Although this is one of the better answers given to this question the last paragraph somewhat conflates conceptual and empirical facts, as did the majority of answers to this question.  A fact is empirical to the extent that it can be confirmed or disconfirmed by sensory information.  So beliefs about cat behavior are still empirical.  Conceptual facts are those that are difficult or impossible to confirm or disconfirm on the basis of sensory information.  For example, the claim that a cat does not have nine lives may be conceptual because it is based on the conceptual fact that dead things do not come back to life.  This is a conceptual fact because any cat that appeared to do this, would normally be presumed not to have been dead after all.)

Question 4

What is circular reasoning?  Why is it a problem?  How does this problem figure in to our understanding of scientific confirmation?

1. Circular reasoning is any reasoning in which the conclusion is presupposed by one or more of the premises.

2. Circular reasoning is a problem because reasoning is normally given in support of a conclusion when the truth of the conclusion is at issue.  Reasoning that simply restates the conclusion does not provide a rational basis for accepting the truth of the conclusion.

3.  Hume pointed out that all inductive arguments depend on the assumption that the future resembles the past.  For example, if we reason:

• In the past, the sun has always risen in the east and set in the west.

• Therefore, tomorrow the sun will rise in the east and set in the west.

We are basing this argument on the suppressed premise:

•  If something has always happened a certain way in the past, then it will continue to happen that way in the future.

Hume pointed out there is no non circular way of justifying the claim that the past is a reliable guide to the future.. 

For example, the argument:

• In the past, the future has always been a reliable guide to the past.

• Therefore, in the future the past will be a reliable guide to the past.

also relies on the same suppressed premise.

This is important for understanding the nature of scientific inquiry.  Science can not prove (non circularly) that the past is a reliable guide to the future.  It simply proceeds on the assumption that this is so.  Fortunately, this assumption is universal, and it has worked out pretty well...so far.

Question 5

Summarize the concept of falsifiability and it's importance.  How does the Quine-Duhem thesis relate to the difficulty of charging someone with having an unfalsifiable view?

Summary:  A person treats a belief as falsifiable if she can recognize evidence that tends to disconfirm, or falsify, the belief.  Someone who holds a belief regardless of the evidence presented against it, is said to hold it unfalsifiably.

Importance:  Karl Popper claimed that all scientific theories, even those we regard as most highly confirmed, must be falsifiable in principle. This distinguishes a scientific attitude from an ideological one.  The latter is characterized by holding fast to certain basic beliefs or principles regardless of what others may say to persuade one to think differently.

Relevance of Quine-Duhem.  According to Quine-Duhem, theories can not be tested individually, but only as a group.  If this is correct, then falsification is a more complicated notion than represented above.  Specifically, someone who appears to hold theory T unfalsifiably, may in fact be simply interpreting contrary evidence as evidence against an auxiliary theory T' rather than T. 

For example:  Consider theory T: All human behavior is selfish.  Someone who holds this view falsifiably will recognize some forms of behavior as unselfish, but will simply deny that humans engage in such behavior.  However, she will hold other auxiliary hypotheses and theories as well.  For example, she may hold T': People usually know what is good for them.  Hence, any apparent example of unselfish behavior may be counted as evidence that falsifies T' rather than T.  E.g., A man who dies rescuing a child he doesn't know may simply be presumed not to have realized the risk he was taking at the time.

Question 6

You and your friend are sitting on opposite sides of a bus going  60 mph down the freeway.  You are throwing a tennis ball back and forth across the aisle.  Explain the relevance of this situation to one of the main arguments for believing that the earth is stationary.

One argument proposed in ancient times for believing that the earth is stationary runs as follows.  Assume that the earth is moving.  Then if a person throws an object straight into the air, the person, who remains on the moving earth, will move away from the ball, while the ball returns to the point in space from which it was tossed.  In fact, this does not happen.  Rather, the ball falls straight back down to the person who threw it. Thus, the earth is not moving.

This reasoning is based on the view that an object thrown straight into the air will return to the point from which it is thrown (unless it is interfered with in some way).  The flaw in this view may be appreciated as follows.  If a person riding on a skateboard over a stationary earth were to throw a ball  straight  into the air, the ball should, on the ancient view, return to the point on earth from which it is thrown.  In fact, the ball will return to the skateboarder herself, following a parabolic path rather a straight one.  This is explained by the fact that the tossed ball still has the linear velocity of the skateboarder, and it approximately retains that velocity during it's flight. 

The bus example provides a similar counterargument.  The ancient view predicts that a ball tossed across a forward moving bus will arrive at a point toward the back of the bus.  But this is not what we observe.  From within the bus, the ball is seen to move in a straight line to a point on the other side. From outside the bus, the ball appears to move diagonally forward to precisely the same point, since that point moves forward as the ball is traveling across the aisle.  Again, this is explained by the fact that the tossed ball has, and approximately retains, the forward velocity of the bus.

Question 7

Is the Copernican system simpler than the Ptolemaic system?  Explain why or why not.  (Note due date change to accommodate study schedule for midterm.)

The Ptolemaic system is geocentric; it places the earth at the center of the universe. The Copernican system is heliocentric; it places the sun at the center of the universe.  Both systems are reasonably faithful to the available data, and both preserve two important conceptual assumptions: (1) the planets all move in perfect circles (2) the planets always move at the same rate (i.e., they neither speed up nor slow down.)

At certain  times of the year planets appear to move backwards.  This is called retrograde motion.  In order to explain this appearance in a way that preserves the conceptual assumptions, Ptolemy required the planets to move in epicycles.  An epicycle is a smaller orbit that occurs within a larger orbit.  During an epicycle, a planet will, from a stationary earth perspective, appear to be moving backwards, even though the center of the larger orbit continues to move uniformly forward. 

Epicyclic motion alone, however, did not preserve circular planetary motion around the earth.  To preserve the perfect circle assumption Ptolemy proved the existence of a geometric point within the larger orbit, around which the planet moved in a perfect circle. This point was called an eccentric.

Even with these modifications, uniform motion was not preserved.  Ptolemy achieved this by proving the existence of another, distinct point within the larger orbit, around which the planet was moving uniformly.  This point is called an equant.

Copernicus' system did not require epicycles to explain retrograde motion, nor did it require equant points to preserve uniform motion, and this is why it is sometimes represented as simpler the the Ptolemaic system.  However, the Copernican system was not able to dispense with epicycles or eccentrics, and in fact the epicyclic motion he required is at least as complicated as the epicyclic motion required by the Ptolemaic system. 

Question 8

Summarize the impact of Galileo's discovery of the phases of Venus.  (Student Sample)

The foremost impact of Galileo’s discovery of the phases of Venus was that it disconfirmed the standard, widely accepted Ptolemaic theory of the heavens.  Instead, the discovery lent empirical evidence in support of a sun centered solar system.  The sun center system, as postulated by either Copernicus or Kepler, predicted the full range of phases that Galileo observed.  The Ptolemaic, Earth centered system, in contrast, predicted that only the crescent phase of Venus should be visible.  

The fact that Venus never appears far from the sun can only be explained in the Ptolemaic system by aligning the sun and Venus along a linear path so that Venus’s epicycle swings it from side to side across that linear path.  However, that solution for explaining Venus’s position in the sky relative to the sun also requires that only a small crescent portion of the sphere of Venus can be illuminated when viewed from the Earth.  That Venus exhibits the full range of phases provides empirical disconfirming evidence against the Ptolemaic theory.  

The heliocentric theory accounts for Venus’s position in the sky relative to the sun by placing its orbit inside that of the Earth’s orbit. In addition, because the orbit of Venus is interior to the Earth’s, one would expect to see the full range of phases as Venus orbits the sun.  Moreover, the noticeable size difference between Venus’s full phase and its most crescent phase is also accounted for naturally under the heliocentric theories by being, respectively, furthest away from the Earth and closest to the Earth.

Nonetheless, the phases of Venus underdetermine that a heliocentric system is essential.  The Tychonic system, which is an Earth centered theory, also accommodates the observational data by having Venus and Mercury orbit the sun much as our moon orbits the Earth. 

Question 9 

Student Answer

How did changing views about the size of the universe and ultimate constituents of the universe figure in to the transition from the Aristotelian to the Newtonian worldview?

Changing views about the size and ultimate constituents of the universe created explanatory dilemmas and hastened the transition from the Aristotelian worldview to the Newtonian worldview.

 Aristotle thought that the universe was relatively small, with a stationary earth at the center and the sphere of the fixed stars as the outermost boundary. But with the advent of the telescope, Galileo discovered innumerable stars, indicating that the universe was much bigger than previously thought and perhaps infinite.

The growing belief that the earth was not the stationary center of the universe and instead orbited the sun also contributed to the image of a vast universe. If the earth were traveling hundreds of millions of miles in its orbit and we still were not observing stellar parallax--stars apparently shifting as we viewed them because of the earth's motion--it meant the stars must be incredibly far away.

Ptolemy's argument from stellar parallax in support of a stationary earth also suffered. Ptolemy contended that if the earth orbited the sun, we should experience stellar parallax. Because we did not, it meant either the stars were unbelievably far away or the earth was stationary. Now that the idea of a stationary earth was waning, it meant, in a Ptolemaic sense, that the stars were unbelievably far away.

A heliocentric universe without bounds rather than one that was geocentric and peripheral undermined the core of Aristotle's worldview. His concept of basic elements earth and water, along with heavy objects, moving naturally toward the center of the universe and the elements air and fire moving away from the center would not work. Neither would another element, ether, causing perfectly circular movement for the planets and stars. Aristotle's essentialistic, teleological vision was questioned.

The notion of an infinite universe became more comprehensible with the philosophical-religious views of de Cusa and Bruno, who said such a universe reflected the infinite greatness of God. It also brought back to light the philosophy of atomism, which saw reality as ultimately being composed of atoms and the void. Atoms were considered the smallest possible particles, and they formed the objects of the physical world by congregating. In the void, or empty space, atoms kept traveling in a straight line unless they collided with other atoms.

The claims of atomism could not be observed or verified empirically, but this philosophy provided a philosophical/conceptual base for understanding and expanding upon ideas. The principle of inertia--an object in motion will remain in motion in a straight line unless acted upon by an outside force--fit well with atomism and the prospect of an infinite universe, and the union of these theories led to greater comprehension and acceptance of the concept of inertia.

Question 10

The Michelson-Morley experiments and black body radiation each served to undermine an important conceptual truth of the Newtonian worldview.  Identify each truth and explain how this occurred in each case.

The Michelson-Morley experiment was performed on the basis of the presumed conceptual truth that a wave is a disturbance in a medium.  Specifically, Michelson and Morley assumed that light waves travel through a medium called the ether.  Michelson and Morley designed an experiment to detect the ether.  Essentially the design of the experiment was to emit two light waves from a single source. One wave was to be emitted parallel to the path of the earth through the ether, the other perpendicular to that path.  Using a device called an interferometer, the waves were reflected back to the source.  Michelson and Morley reasoned that if the earth were moving through the ether, then the light emitted perpendicular to the path of the earth will travel a different distance through the ether than the light emitted parallel to the path of the earth. This difference in distance should be detectable by the interferometer in the light rays being out of phase on their return to the source.  However, no such difference was detected, and Michelson and Morley's experiments were ultimately understood as evidence that light waves are propagated in the absence of a medium.

A black body is a theoretical entity that below a certain temperature absorbs light of every wavelength.  As a block body increases in temperature it emits light of every wavelength.  The conceptual truth at stake here is that nature is a continuum.  Specifically, continuous changes in the temperature of a black body will generate continuous changes in wavelength.  The model is accurate for long wavelengths, but fails catastrophically, beginning with the shorter wavelengths of the ultraviolet spectrum. The problem, known as the ultra-violet catastrophe, is that the Newtonian model predicts that as the wavelengths of light emitted become shorter, the associated energy level tends toward infinity.  This was regarded as an absurdity, and also highly disconfirmed by experiment on imperfect black bodies.  Max Planck developed a predictive model predicated on the assumption that electromagnetic radiation is not continuous, but can only be emitted in discrete packets or "quanta", an idea which ultimately requires a fundamentally different view of the microphysical structure of the universe.

Question 11

What does the principle of relativity contribute to our understanding of the discovery that the earth moves around the sun?  Explain.

According to one version of the principle of relativity, there is no absolute reference frame from which to describe the motion of objects.   To move is simply to change ones position with respect to other objects, and this change may be described differently depending on the reference frame one adopts.  In retrospect, then, the Aristotelian claim that the earth is stationary simply expresses the choice of earth as a reference frame from which to describe the motion of other bodies.  By contrast, the claim that the earth and other planets move about the sun simply expressed the choice of the sun as a reference frame.  According to the principle of relativity, this latter claim ranked as a discovery only because the heliocentric model made the paths of the planets and other celestial bodies easier to describe and comprehend. 

Question 12

The fact that moving clocks run more slowly than stationary clocks implies that moving lengths are shorter than stationary ones.  Why?

Assume the existence of two synchronized clocks A and B a finite distance D apart.  Assume that A moves toward B at close to the speed of light, covering the distance D between them in T seconds, as measured by stationary clock B.  By the time dilation hypothesis, clock A will register the time elapsed in T' seconds where T' is less than T. 

However, due the principle of relativity, clock B may be equally well described as moving toward  clock A.  This means B must traverse the distance between A and B in T' seconds as measured by clock A.  But since (1) t' is less than T and (2) the velocity of B moving toward A must be the same as that of A moving toward B,  this is only possible if the total distance covered by moving clock B is less than D.

Hence, if moving clocks run more slowly than stationary clocks, then the principle of relativity requires that moving lengths are shorter than stationary ones.

Question 13 

Explain how thinking differently than Newton about the concept of acceleration allowed Einstein to think differently than Newton about the concept of gravity.  Be clear about what these differences are.

Student Sample

In the Newtonian worldview,  the notion of universal gravitation is captured by the attraction between two objects. Moreover, the force between the objects is dependent on their masses, and their distance.  The more massive the objects are, the greater the attraction; the further they are apart, however, the less the attraction becomes. This is captured by the law of universal gravitation: F=G m1m2/r where m1 and m2 represent the objects' masses and r their distance.

There are, however, two unexplained consequences. First, the masses in law of universal gravitation always turn out to be the same as the mass in the second law of motion, which describe acceleration force; however, they are not conceptually connected at all. Secondly, this view of gravity entail the "spontaneous action at a distance," which is just as fantastic as the Aristotelian view that objects have desire.  Moreover, this is particularly problematic in the Einsteinian worldview, since there is no absolute simultaneity.  It should be noted that even Newton himself only adopts an instrumental attitude toward the existence of gravity.

Einstein 's insight is to point out that there is really no difference at all between  the effect of gravity  and the effect of acceleation. He uses quite a beautiful thought experiment to  illustration this point. For the sake of brevity, it basically involves asking one to imagine being in a room sitting on the surface on the earth, thus feeling the gravitational pull, and then imagine a room in empty space that is being push up. Einstein then asserts that there is no way we can tell the difference when being placed one of these room.

This experiment is meant to illustrate the principle of equivalence, which states effects due to gravitation and acceleration is indistinguishable. While such phenomenon is not explained in the Newtonian worldview, in the Einsteinian view, gravitation is not explained by some sort of magical attraction between objects, but by  the curvature of spacetime caused by the sun - planets are actually moving in a straight line, but only appear to be elliptical.

Question 14

Identify the error made in the following statement and correct it:  "What makes the results of the quantum experiments so strange is that they are entirely unpredictable.  It seems that we can never know from one experiment to the next how subatomic particles are going to behave.  This contrasts starkly with the deterministic picture of the world offered by both Newton and Einstein."

The results of experiments in quantum experiments are repeatable and therefore predictable.  For example, in the famous two-slit experiment we can reliably predict that photons will behave as waves when they are not detected and behave as particles when they are detected.  This is not what contrasts with the deterministic picture of the world offered by Newton and Einstein.

What does contrast with this picture is the idea that the physical state of a particle (e.g., it's location or velocity) does not exist prior to measurement.  Determinism holds that particles have determinate properties regardless whether they are measured.  But according to quantum mechanics, if a particle is not measured, then its actual behavior is fully represented by a set of equations representing its behavior in purely probabilistic terms.

Question 15

Explain the importance of the locality assumption in the EPR paradox. Explain how the Bell/Aspect results challenge the locality assumption.

The locality assumption holds that all effects are local in nature. In other words, it is impossible for objects remote in space and time to affect each other except by propagating these effects through contiguous spatial localities.  Among other things, the locality assumption implies that the instantaneous communication of information is impossible.  Information must be propagated through space and time by a process that requires space and time.

The EPR paradox may be stated as follows:  It is theoretically possible to generate photons in such a way that we know them to be in identical physical states, though we do not know which state until they are actually measured.  Imagine that two such photons A and B are generated and sent to opposite ends of the universe.  According to quantum mechanics, it is not only the case that the states of A and B can not be know prior to measurement, but that they do not even have these states prior to measurement.  But this violates the locality assumption as follows:  Since we know that A and B are in identical states, measuring the state of particle A instantaneously confers the same state on B.

Einstein believed that the violation of the locality assumption implied that the quantum mechanics is fundamentally flawed or incomplete. Unfortunately,  Einstein's thought experiment has no empirical ramifications, so it is untestable.  However, Bell, discovered that the equations of quantum mechanics actually do make predictions that violate the locality assumption.  Specifically, they predict a certain kind of statistical correlation between the measurements made of photons in twin-states that would violate the locality assumption.  Eventually, Alain Aspect was able to perform this experiment, and the predictions of quantum mechanics were vindicated.

Hence, what was initially posed as a refutation of quantum mechanics ended up being evidence that the locality assumption is false.