Let’s talk about what the phrase “philosophical knowledge” might mean, and in the process we will give a short introduction to some fundamental issue in the study of knowledge (which is called epistemology), issues like the Gettier problem, the internalism/externalism debate, and skepticism/scepticism.  There are three things that we are referring to by the title “philosophical knowledge.”  Perhaps the most obvious is beliefs about philosophical matters.  Some of the basic issues in philosophy are the nature of the mind, the foundations of ethics, the principles of logic, and the essence of knowledge.  When we talk about philosophical knowledge we can refer to the beliefs people have about these issues.  So, for example, a person may proclaim herself to be a physicalist with regard to the mind.  This person would claim to have philosophical knowledge when she claims to know physicalism is the best way to go in philosophy of mind.

When we say “philosophical knowledge” we can also refer to central issues within the study of knowledge itself.  The study of knowledge is called epistemology.  Don’t stumble over this word.  It simply refers to the study of how people know what they know.  There are certain things that we want to know about knowledge when we investigate it.  We want to know what its nature is, that is, what are its essential components.  And we want to know how we can keep knowledge in the face of the most extreme challenges of skepticism and disagreement.  Below is an overview of these issues that will be expanded in the coming months.

Another thing referred to by the phrase “philosophical knowledge” is best understood in juxtaposition to religious knowledge.  The study of knowledge today is done in the context of discussions about beliefs that aren’t religious, very ordinary beliefs.  For example, right now I believe that my car is parked in the driveway.  This isn’t a religious belief.  It doesn’t make any reference to religious notions, for example, of Allah, Shiva, or religious experience.  We can call the object of philosophical knowledge in this sense ordinary knowledge in distinction from religious knowledge.

The essence of knowledge

Traditionally, many people believe that any knowledge is composed of three things:  belief, justification, and truth.  These are thought to be three necessary conditions for knowledge in the sense that they have to be present in order for there to be knowledge.  But they have also been thought to be sufficient conditions as well, in the sense that when they are present, one surely has knowledge.  Simply put, a belief is an attitude that a person has towards some statement about the world.  So, here is a statement about the way the world is:  My car is in the parking lot.  When I say I believe this statement I am saying that I affirm it as true.  And justification is the support we have for thinking a belief is true.  I discuss these three components of knowledge in much more detail in the book pictured above, The Epistemology of Religious Disagreement.

Just having a belief and justification for it doesn’t make it knowledge.  The belief has to be true.  For example, no matter how much justification a three-year-old has for believing there is a Santa Claus who brings gifts to all the good children of the world, that child cannot know this simply because it isn’t true.  If just one of the three necessary components is missing, there is no knowledge.

Likewise, just having a true belief doesn’t give us knowledge either.  Even when a belief is true, if I came to that belief in a completely random way without justification, then I don’t know it.  Justification is the support one has for a belief that ensures the belief is more likely true than false.  Say I come to a fork in a road when trying to get to a school.  To determine which road I believe is the right road I get out a coin and flip it.  If the head side shows up (in the USA coins have a picture of a famous person’s head) I would believe the left road is correct.  If the other side shows up, I would believe the right side is the correct road.   The coin comes up heads, and so I believe the road on the left is the correct road, and I am actually right.  Even though I have a true belief, I don’t have knowledge because I really don’t have any justification.  Most people would recognize the flip of a coin to be a random process inadequate for justification.

Many have challenged the necessity of these three things for knowledge.  But let’s look at the best challenge to the sufficiency of these three things.

The challenge of Gettier

In 1963 Edmund Gettier in a published paper just barely three pages long challenged the nice clear understanding above (standard at least since Plato) of the nature of knowledge.  Gettier gave examples of situations where one could have all three conditions met, but still not have knowledge.  The three things may be necessary for knowledge, but they don’t appear to be sufficient.

Consider the following situation:

Fake Barn Country:  A man, say Mustafa, is driving along with his son in the country.[i] He points to a barn and says, “My son, this is a barn.” Now it is really true that it is a barn. Mustafa certainly has a belief that it is a barn. And he certainly has much good justification for thinking it is a barn. Let’s just say he has worked around barns all his life, and he only recently moved to the city. Now to the crucial part of the story: Unbeknownst to Mustafa, Hollywood has been filming in the area and has been setting up fake barns to supplement the real ones. It turns out that the barns just to the right and left of the barn he pointed to are fake. Mustafa just as easily could have pointed to one of the fake barns had he been driving a little faster or a little slower, or had he been a little distracted by something on the road. It is rather lucky that he pointed to the actual barn.

Here Mustafa may have a justified true belief about the barn.  But he doesn’t know it.  There is just too much luck involved in this situation.  He could have easily chosen a nearby barn, in which case he would have had a false belief.

The nature of justification

Earlier we said justification is the support one has for a belief making the belief more likely true than false.  There is a tremendous amount of debate about how to understand justification.  One of the biggest controversies in epistemology today revolves around the debate between internalism and externalism as different ways of understanding justification.  We can establish a good sense of what this controversy is all about by referring to the analogy for justification that we have been using.  Just like a good rope tether for the boats pictured in Istanbul (See the front cover of the book in the top left corner) holds them in one’s possession throughout many weather conditions, so too the justification we have for our beliefs holds us to them throughout many of the challenges we experience.  Justification connects us to the belief with its assurances that the belief is more likely true than false.  Like the good rope tether, justification anticipates and avoids situations where the person would be mistaken.  Poor justification doesn’t hold us very strongly to our beliefs. Both sides of the debate assert that justification, the tethering, is what holds one connected to a true belief throughout challenges. The controversy rages over how the tethering function of justification works in order to hold people to a true belief.

To get a better sense of what the two different views of tethering think, let’s pay attention to the spatial reference within the words themselves.  The words “internalism” and “externalism” suggest that the debate has to do with where justification is located, whether inside or external to something.  We can take our lead from this.  What the tether is, and how it works, has everything to do with where it is located.  The “inside” refers to something that is going on within the first-person cognitive perspective of a specific individual pursuing knowledge.  What justifies a belief for an internalist has everything to do with what is inside this first-person perspective.  Being inside in this way is a necessary condition for justification.  So, on one version of internalism, I can’t know my car is in the parking lot unless I have good reasons for thinking this; reasons are the sort of thing that people are aware of, and this awareness of reasons means that those reasons are part of the first-person cognitive perspective of a specific individual.

The externalist thinks being inside—in the earlier sense of “inside”—isn’t a necessary condition for justification.   In other words the externalist thinks what justifies a belief doesn’t have to be within the first-person cognitive perspective of the individual pursuing knowledge.  To say this in a positive way, what justifies can be external to the cognitive perspective of the specific individual.  One version of externalism focuses on reliability.  A belief-forming process can be reliable without having good reasons for thinking it is reliable.  So, a belief can be justified without the thing that justifies being internal to the first-person cognitive perspective.



No issue has occupied epistemologists more than the problem of skepticism; and for good reason, since the seductive siren song of the skeptic presumes to show nobody has any knowledge. The skeptic claims we don’t have knowledge because minimal standards of justification aren’t met.  In a popular version of skepticism, the skeptic works her magic by convincing the opponent both that he doesn’t know some possible, alternative world isn’t happening, and that this deficiency nullifies any ordinary knowledge.

Let’s look at the logical structure of the problem as discussed in analytic epistemology today. The problem of skepticism is nicely described as revolving around three statements displayed in symbolic notation:

1)       K(p)

2)       ~K(~s)

3)       K(p) → K(~s)

K = Knowledge

p = Some ordinary statement.

s = Some skeptical scenario

~ = not

→ = If . . . , then . . ..

The first statement says in ordinary language, “I know that p.” The “p” is some ordinary proposition. One ordinary proposition is, for example, “I have a hand in front of my face right now,” or “My computer is on the table.” K(p) simply says, for example, “I know that I have a hand in front of my face right now.” The first statement of the problem of skepticism simply asserts some ordinary, everyday knowledge.

The second crucial statement of the problem of skepticism gets one to entertain a skeptical scenario. For example, think of the movie “Matrix.” That movie became famous because of the skeptical scenario that it asks us to consider, and because people recognize that knowledge is fragile in the face of skeptical challenges. The movie asks us to consider the possibility that we are merely in a computer generated simulation of an actual world. We are really bodies in vats used by machines in the not-too-distant future. In the movie the characters are placed in vats and hooked up to electrodes that feed a computer program to them making them believe that they are in a real world when they are only in a virtual world. After watching the movie in Berkeley, California, I remember looking for telltale signs that one is in a matrix, the glitches in the system due to changing software programs, which people ordinary call déjà vu. What the skeptic does is paint a picture of a possible world indistinguishable from the one we think we are in, only in those worlds our beliefs would be false. There is an enticing symmetry between the world one thinks one is in and the world painted by the skeptic.

The second component of the problem of skepticism asks one to think about how one justifies the belief that one is not being subjected to some huge deception such as the one in the movie “Matrix.” How would one prove that one isn’t? Many people find it quite intuitive that they can’t prove, or even adequately justify, that they aren’t in some such bizarre situation. We simply don’t know that we aren’t in one of these situations painted by the skeptic. There are many other skeptical scenarios. For example, the possibility that you right now are hallucinating, dreaming, or being hypnotized. My personal favorite: The possibility that we are simply ideas in God’s mind right now before God creates an actual world. It is pretty hard to know that these things aren’t happening. You should see the common structure of all skeptical moves as ~K(~s), which says, for example, “I don’t know that I am not in a matrix.” Every source of support for a belief one engages in the actual world would be also engaged in the possible world painted by the skeptic. The skeptic exploits the fact that the skeptical scenario appears so similar to the actual world.

The siren song of the skeptic doesn’t end just by pointing out symmetry between two situations, nor only by demonstrating that the similar processes produce conflicting results, nor even just by showing how one’s sources of support are incapable of anticipating and avoiding the skeptical error possibilities. Even more, the skeptic, in a third move, tempts one to think that the sources of support one has for an ordinary proposition imply that one can anticipate and avoid the situations of error described by the skeptic. But of course they can’t; but this gives away too soon the rest of the story. Think, now, about the implication the skeptic convinces us of. It can be expressed in symbolic form by the following statement: K(p) è K(~s). You will notice that the third statement links the first statement and part of the second one through a conditional statement. It says, in ordinary language using G.E. Moore’s example of an ordinary statement, “If I know that I actually have hands, then I know that I am not in a matrix.”

The third component of the problem of skepticism engages what is called epistemic closure:

Epistemic Closure:

One knows whatever is implied by what one knows.

Let’s just say, for example, that a person knows that her computer is on the table. It seems implied by what she knows that the computer is not a matrix simulated computer, or that it is not just a figment of her imagination. Her knowledge that her computer is on the table implies that she is not in a matrix world.

The skeptic uses the closure principle to argue from modus tollens as follows:

K(p) → K(~s)



For example, the skeptic could say, if she knows that her computer is on the table, then she knows that she is not in a matrix. But, she doesn’t know that she is not in a matrix. So, she doesn’t know that her computer is on the table.

[i] This is a modification of Alvin Goldman’s original use of this example in Alvin Goldman, “Discrimination and Perceptual Knowledge,” Journal of Philosophy 73 (1976): 771-91.

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