It seems to me that this avoids the self contradictory "everything is uncertain, even uncertainty" while allowing agnostic positions, by allowing only uncertainty as the only thing certain, sort of the base case for everything.
Edit: Based on the first answer, the way I would formalize is: "Certain(x)" and "x = !Certain(y)" where "y = !x"
Actually it may not be a contradiction:
We are only certain of progressive change. This change manifests itself as the progression of one self evident truth to another: A -> B -> C...
This progressive change observes a linear continuum, as one self evident truth progresses to another.
This linear continuum, as progressive axioms, is constant in both an abstract sense and empirical time (ie one particle moving from one position to another always has a straight line between points even if the pattern is zig zagging.).
This linear continuum observes form and function as the same thing. So while we may have variously changing self evident truths, these truths exist recursively under a single platonic form.
Each change effectively is composed on infinite immeasurable changes (ie zeno paradox or a line composed of infinite lines) this necessitating infinite change as indefinite change or "no change.
Change is that the observation of multiple parts. For example one picture inverting to another picture observes static pictures but the perceived movement only occurs because of the multitude of pictures. Change is thus grounded in the inversion of one phenomenon into many. One picture into another, the position of one particle into another position, one emotion into another emotion, etc.
Change and no change, using a line as an example, is assumed through form alone. It is the dualism between one and many forms that allows change and no change to be observed. However this dualism is synthesized under the "form" itself as a "boundary of movement".
This can be observed through the platonic forms as consisting of many forms or the process of actualization, in aristotelian thought, as matter existing through form where potentiality (ie mass) exists through form as movement.
I hope this makes sense, I may have to clarify some points.
Everything is uncertain, including uncertainty, for the simple reason that your brain is just a machine, and machines can fail for a variety of reasons. If you're willing to accept that something as simple as 2+2=4 is slightly uncertain (and you should be) then you should be willing to accept that the reason 2+2=4 is uncertain is also uncertain. Consider that "the reason 2+2=4 is uncertain" is significantly more complex reasoning than "2+2=4" itself, and more complex means more error-prone.
Anyway, why is everything uncertain? Because your brain is a machine, and machines are fallible. Let's start by looking at how silicon computers are fallible. Silicon computers are much more reliable at accurate math calculation than your brain is, and yet you cannot fully trust the result of a mathematical calculation done on a computer.
So those are some examples of how a machine can fail at any calculation. Your own brain is a machine too, and a much less precisely designed one than a computer. Your brain makes mistakes at a much greater rate than a computer.
Of course, if your brain's operation is fallible, then any calculation or reasoning you do mentally, no matter how simple, might in fact be an error, as it is the result of your brain's operation. You have no way of verifying or checking this reasoning except by ultimately relying on your brain, so any verifying/checking process is also fallible. Perhaps you can get very close to certainty, but it is irrational to suppose you ever have perfect certainty.
