Are you absolutely certain about your certainty? If certainty was your criteria for knowing a genuine belief, would you ever be able to know or believe anything? There are many things in our day to day experience that we think we certainly know. Then upon closer investigation we found that we were wrong. Perhaps we didn’t have enough information about the thing in question, perhaps our perceptual understanding failed us, there are many factors that could cause is to be wrong about something that we were quite certain about. Epistemic questions about certainty can get pretty dicey but they are deffinately important. As it turns out what ever someone believes to be the case epistemologically will ultimately determine that “facts” of their experience. Take Rene Descartes for example. He writes in the Meditations:
“…in as much as reason already persuades me that I ought no less carefully to withhold my assent from matters which are not entirely certain and indubitable than from those which appear to me manifestly to be false, if I am able to find in each one some reason to doubt, this will suffice to justify my rejecting the whole.” –Descartes, Meditations
In his work On Method, as well as the Meditations, Descartes appeals to a principle of epistemic certainty as a prerequisite for genuine knowledge. In other words Descartes’ project necessitates evidence that is indefeasible much like the types of evidences we find in mathematical proofs. His major premise can be understood as: in order to know P one must be absolutely certain of P (we will refer to this as the “certainty principle” [CP]). Thus, if there exists, even the smallest possibility that your knowledge of P is not absolutely certain then you are not in any epistemological state to know P.
One example of this that has been give is The Lottery Argument. No matter how strong your evidence is that your ticket won’t win (or in this case the odds of winning are against you) you’re never absolutely certain that your ticket won’t win.
This is the same principle being advanced in the skeptical thesis (ST). That is, if you cannot claim to know something absolutely then you cannot claim to know it at all. When we take honest inventory of the beliefs we posses the number of those beliefs that we can be infallible about are very few and far between. But does this warrant skepticism? Some skeptical arguments leave us with no claim to knowing anything about the external world unless we have absolute certainty. On this set of beliefs one could never truly know if she is walking outside in the sun or a brain in a vat. Perhaps the question over the validity of the certainty principle as the only claim to knowledge is the wrong question to be asking.
A more desirable epistemic state would be one in which belief in P can be accepted as knowledge in spite of the absences of certainty providing that P is true. This is called the fallibilist principle of knowing (FPK). The key difference between fallibilism is the notion of certainty. Epistemic fallibilism does not require your evidence for P to be indefeasible or infallible but it still treats knowledge as being factive. For example you might look into the sky and notice a full moon. You suddenly realize that every time you noticed a full moon in the past it was followed by a high tide. You take your finding to the library and notice the phenomenon has been taking place centuries. You further read about the moon’s gravitational pull on the earth causing high tides. Based on this evidence you believe that a full moon always precedes a high tide. However, there is a chance you might be wrong; moreover, your evidence is defeasible. That being the case the fallibilist would say you are still in a desirable epistemic state to know that a full moon precedes a high tide.