The Regress Argument for Skepticism



1.  In order to know something, it’s not enough just to believe it – you have to have a good reason to believe it.


In other words:


For any proposition p, if S knows that p,

then S has a good reason to believe that p (S is justified in believing that p).


2.  A good reason to believe p can’t be p itself (that would be circular reasoning!).


3.  Rather, a good reason to believe p must be something else you know that supports p.


In other words:


For any p, if S has a good reason to believe that p, then S knows some q such that q supports p and q ¹ p.


4.  But q is not known unless it is supported by knowledge r, where r is not identical to any other member of the chain (in order to avoid circular reasoning).

And so on…


5.  Therefore, no belief is known unless it is supported by an infinitely long chain of other beliefs.


6.  But that’s an impossible condition for a person to meet!


Being finite creatures, we can’t have infinitely many different beliefs.

Even if we did, we would never be able to satisfactorily give a justification for any of them, since that would require infinite time.


7.  Therefore, we don’t know anything.






Is the Regress Argument self-defeating?


If the conclusion were true, then we wouldn’t know that the conclusion is true (because we wouldn’t know anything).  This is odd, because the point of the argument is to establish that the conclusion is true.


The Regress Argument seems to be valid.  Yet, according the conclusion, we don’t know this either, nor do we know that any of the premises are true…


Thus, the minute we accept the Regress Argument, our justification for accepting it is undermined.


There are (at least) two ways we could look at this: 


(i) The Regress Argument does not really give us a justification for accepting its conclusion (despite the appearance to the contrary).


(ii)  The Regress Argument does give us a justification for accepting its conclusion—but only if we haven’t accepted it yet.  Once we accept the conclusion, the justification for it disappears, as if we had used a ladder to climb onto a roof and then kicked it away.


Either way, the conclusion of the Regress Argument is absurd; it is perhaps the most absurd conclusion possible.  To see this, consider a different absurdity: black is white.  Why is this absurd?  Basically, because we know that it is false.  But this response presupposes that we know something.  The conclusion of the Regress Argument denies that we know anything


The Regress Argument is a paradox—an argument, each step of which is very plausible, yet leads to a conclusion that seems absurd.




Responses to The Regress Argument




Response 1:  Foundationalism



Foundationalism denies premises 2 and 3 of the Regress Argument.



For a Foundationalist (e.g. Descartes), beliefs are divided into 2 categories:


            Nonbasic beliefs – these are justified by other beliefs


                        - most of our beliefs fall into this category


Basic beliefs – these are sometimes said to be “self-justifying”; it is perhaps more accurate to say that they are justified by something other than beliefs (experiences and rational insights)


– every nonbasic justified belief is justified by other nonbasic beliefs, which in turn are justified by other nonbasic beliefs…until we get to the basic beliefs


– basic beliefs are not justified by other beliefs



Descartes’ Strategy


“Physical things exist.”



“God exists and is no deceiver”



“What I clearly and distinctly perceive is true”



“I exist”
















Do Foundationalists endorse circular reasoning?


No, not really.  Some philosophers describe basic beliefs as “self-justifying”.  This makes it sound like a Foundationalist would think the following is a good argument for some belief P:


1)  P


2)  Therefore, P


First, if P is a nonbasic belief, then by definition it does not justify itself.  Only basic beliefs are said to be self-justifying.  Second, it is misleading to say that even basic beliefs are self-justifying.  Recall the cogito.  Descartes does not say that it justifies itself; rather, it is justified by “clear and distinct perception” or “the light of nature”.  The same goes for his other basic beliefs.  What justifies a basic belief, then, is a type of conscious mental episode which is not itself a belief.


Building from the Foundations:  Empirical Basic Beliefs


Descartes identifies clear and distinct rational insights as basic beliefs, and tries to build up his knowledge of the world from these.  He hit some snags, to say the least.  But other philosophers have held that our sensory experience is a source of basic beliefs that can provide us with knowledge of the world without going through the circuitous route of proving the existence of God first.


Consider the following potential beliefs, none of which are rational insights:


“There is a brown rectangular shape in my visual field”

“I seem to be walking to class”

“I seem to be in a lecture”

“I feel a sharp pain”

“I hear a pleasant sound”


Suppose these beliefs are justified by our sensory experience.  Could we be deceived or otherwise mistaken about any of them?


In general, we are deceived when things are not the way they appear or seem.  However, if we are cautious, and merely report the sensations themselves, and the way things seem to us, then we will not be mistaken.  Can these cautious statements serve as a foundation for our knowledge of the world?


Berkeley and Phenomenalism


[Note:  In PP, Rachels draws a subtle distinction between Berkeley’s Idealism and Phenomenalism.  We will simplify and treat Berkeley as a Phenomenalist.]


George Berkeley (1685-1753)


But, though it were possible that solid, figured, movable substances may exist without the mind, corresponding to the ideas we have of bodies, yet how is it possible for us to know this? Either we must know it by sense or by reason. As for our senses, by them we have the knowledge only of our sensations, ideas, or those things that are immediately perceived by sense, call them what you will: but they do not inform us that things exist without the mind, or unperceived, like to those which are perceived. This the materialists themselves acknowledge. It remains therefore that if we have any knowledge at all of external things, it must be by reason, inferring their existence from what is immediately perceived by sense. But what reason can induce us to believe the existence of bodies without the mind, from what we perceive, since the very patrons of Matter themselves do not pretend there is any necessary connexion betwixt them and our ideas? …

In short, if there were external bodies, it is impossible we should ever come to know it; and if there were not, we might have the very same reasons to think there were that we have now.






We are aware of our own ideas—our own experiences, the way things seem to us.


We are not aware of the existence of a material world, and we have no evidence that it exists.


Hence, we should not believe in the material world.


Phenomenalism is not Skepticism, nor does it imply that most of our beliefs are mistaken.


Berkeley:  “…[W]e ought to 'think with the learned, and speak with the vulgar.' They who are convinced of the truth of the Copernican system do nevertheless say 'the sun rises,' 'the sun sets,' or 'comes to the meridian; and if they affected a contrary style in common talk it would without doubt appear very ridiculous. A little reflection on what is here said will make it manifest that the common use of language would receive no manner of alteration or disturbance from the admission of our tenets.”


Phenomenalism is an attempt to validate our claims to knowledge about the world by giving them a solid foundation.


According to phenomenalism, we can be confident that most of our beliefs about the world are correct, but we have to understand them in a way that doesn’t require the existence of material things.


So, objects such as trees and books and people do exist.  But they are not material objects.  Instead, they are “bundles of ideas”.


Rachels explains the phenomenalist approach (on page 143): 


a tree is nothing but a bundle of sense-data.  Consider all the experiences you have of the tree:  You see it from different angles at different times, you touch it, you hear it sway in the wind, and so on.  Consider these together with all the tree-experiences that other people have had.  “The tree” simply is all those experiences, considered collectively.  (A similar analysis, of course, can be given of any other physical object.)”


Problem:  If an object is just a collection of sensations, then there is no such thing as an unobserved object.  This is hardly what you would call “speaking with the vulgar”!


John Stuart Mill:  Objects are permanent possibilities of sensation


In other words:  An object is not just a collection of actual sensations; an object is the experiences that we would have were we in the right position (or, rather, were we to have certain other experiences first)


Question:  What is the metaphysical basis for “permanent possibilities of sensation”?  What is it about the world that makes it true that we would have certain sensations under certain conditions?


The answer which seems obviously correct to most of us:  The world contains material objects that exist independently of us, and these impinge on our senses, causing us to have certain sensations under certain conditions (e.g. when we are nearby).  But this would mean that phenomenalism is false.




The Big Problem for Foundationalism


            There aren’t enough basic beliefs to form a good foundation for our supposed knowledge of the world.  Both Descartes and Berkeley have this problem, though it is manifested in different ways.  In Descartes’ case, he needed to be able to prove the existence of God using reason alone.  His apparent failure to do this left the Skeptic (The demon hypothesis) undefeated.  In Berkeley’s case, he needed to be able to validate our beliefs about ordinary objects using sensory experience alone.  He couldn’t do this because our beliefs about ordinary objects only make sense on the Natural Theory (which entails that they are external, physical objects that can exist independently of us).



Response 2:   Coherentism


            Denies the “non-circular” clause in premise 4 of the Regress Argument


            According to Coherentism, a belief is justified for you when it fits together well with your other beliefs.  Coherence requires that it be logically consistent with your other beliefs, and be supported by them (meaning that the belief in question is more likely to be true on the assumption that your other beliefs are true).  Unlike the foundationalist, the coherentist does not have a strictly hierarchical view of justification.  Coherentists do not assume that there are any basic beliefs.  Even if there are, they do not play a special role in justification—a belief can be fully justified even if it is not supported by basic beliefs at all.  If foundationalism conceives of justification like a building, then the coherentist conceives of justification as something like the surface of a ball.  Each point on the surface is connected to (supported by) other points (some close, some distant), and no amount of traveling along the surface will bring you to point where the connection comes to an end.  Eventually, you will have traveled all the way around and will end up where you started.  Thus, coherentists ultimately do believe in circular reasoning – as long as the circles are big enough.





Pros and Cons of Coherentism


Pros:  (i)  Agrees well with what we actually do when we assess the justification of one of our beliefs.  (ii)  Avoids the problem of foundationalism that there aren’t enough basic beliefs.


Cons:  (i)  Endorsement of circular reasoning is hard to defend.  (ii) There is no guarantee that our justified beliefs are true.  We check one belief against others, but we cannot ever check them against reality. 


This may be a disappointing result, but that’s just the way life is, coherentists say.  If justification required absolute certainty (as the infallible foundationalist claims) then only a very small number of our beliefs would be justified.



Both Foundationalism and Coherentism are examples of internalism, the view that justification of our beliefs must be something internally accessible.  According to the Foundationalist, I can tell whether I am justified in believing something because I can (in theory, at least) ascertain whether it is supported by basic beliefs.  According to the Coherentist, I can (in theory, at least) ascertain whether a belief coheres with my other beliefs.




Response 3:  Externalism


            denies premise 1 of the Regress Argument



Professor Mattey, from fall 2004 lecture notes:


Internalism and Externalism


One of the main disagreements in contemporary epistemology is between the "internalists" and the "externalists." A simple way of distinguishing the two positions is to say that externalism makes at least some attributions of knowledge on the basis of purely external considerations. For example, S was caused to believe that P in a way that involves the truth of P itself. Or S's belief that P was formed in a reliable way. For the internalist, some additional, "internal" factor is always required before knowledge can be attributed to a subject. Generally, this factor involves some "reason" S has to believe that p is true.

It is pretty easy to separate internalists from externalists using a simple test. Are they willing to attribute knowledge to animals and small children, which are both supposed to be lacking with respect to rationality? If they are willing to attribute knowledge to animals and small children (not to mention computers), they are most likely externalists, and if they are not, they are most likely internalists.


Externalists agree with internalists that having a true belief isn’t enough for having knowledge – a third ingredient is needed.  But for externalists, the third ingredient is not a “reason.”  A reason is something that can be found internally—a belief or an experience that the subject can be aware of.  According to externalists, the third ingredient is an external condition that the knower may not be aware of.  There are different externalist accounts of what this condition is.  One of these is


Reliabilism*:  S knows that p if and only if

(i)                 S believes that p,

(ii)               it is true that p, and

(iii)             S’s belief that p is caused by a process that reliably causes true beliefs.


*this is a simple version of reliabilism that has since been improved in several ways.  The simple version will suffice for our illustrative purposes.



Note that according to reliabilism, it does not matter whether I have any other beliefs that can justify the one in question; as long as my belief is true and was formed by a reliable process (e.g. a properly functioning visual system in a normal environment) then my belief is knowledge.


Pros and Cons of Externalism


Pros:  (i) Provides a plausible account of certain types of knowledge (e.g. visual knowledge).  (ii) The externalist condition, when met, rules out the possibility of BVH, or a Cartesian demon, etc.


Cons:  (i) Seems to go too far in making attributions of knowledge.  (ii) We can’t be certain that the externalist condition is met, so there is a sense in which the Skeptic remains undefeated.



The KK thesis:


In order to know that p, it is necessary to know that one knows that p




If S knows that p, then S knows that S knows that p



Foundationalists and Coherentists accept the KK thesis.


Reliabilists deny the KK thesis






The Natural Theory


(as described in PP, P. 149)


Natural Theory is a set of commonsense beliefs that we want to validate by refuting the Skeptic.  None of the “isms” we have looked at have been able to do this satisfactorily.


Rachels p. 152 “from within the point of view provided by [the Natural Theory] we can be confident that we are surrounded by a world of real physical objects…But that is the best we can do.



But what epistemic reason to we have for accepting the Natural Theory in the first place?




The Reliability Dilemma Argument Against Skepticism





Basic Sources of Information (BSI) = sensory experience, memory and rational insight


Reliable = pretty reliable source of true beliefs when used carefully



1.  Either our BSI are reliable or they are not. 


2.  Suppose our BSI are not reliable.


3.  In that case, we have no hope of achieving our basic epistemic goal--we are bound to fare poorly at attaining truth and avoiding error.


4.  Thus, if our BSI are not reliable, then it makes little or no difference to our basic epistemic goal whether we believe they are reliable or not.


5.  On the other hand, suppose that our BSI are reliable.


6.  In that case, we will be more successful at achieving our epistemic goal if we believe that they are reliable.


If we don’t believe this, then we will be less likely to accept the reliable information supplied by our BSI.  Also, not believing in our BSI would tend to undermine our justification for accepting the information supplied by our BSI, with the result that we would lack knowledge even if we had true beliefs.


7.  Therefore, believing our BSI to be reliable can only help us to achieve our basic epistemic goal and will not impede it, regardless of whether our BSI actually are reliable.


8.  Moreover, the belief that our BSI are reliable coheres with our other beliefs.


9.  If believing something helps us to achieve our basic epistemic goal and it coheres with our other beliefs, then we are justified in believing it.


10. Therefore, we are justified in believing that our BSI are reliable.





Copyright © Dan Gaskill 2005