Of course you couldn't *know* that your senses are 100% accurate, because it is not *true* that your senses (or anyone elses for that matter) are always 100% accurate.
Since I can't *know* that my senses are 100% accurate at any point, then I am left to dealing with probabilities (however great the probability, it still isn't 100% certain).
Now you may mean that you can't know anything from your senses because your senses are not always 100% accurate. But if that is what you mean, why assume that knowledge must only come from infallible sources?
knowledge = justified true belief
My problem is that I don't understand how strictly we must define "justified." Is "justified" a matter of probability? Say, 99.5% probable? (Who gets to decide?) Or is "justified" 100% certain? And who can know that anything is 100% certain except for One who is infallible?
That to know something entails having certainty is mainly a Cartesian constraint and has largely been abandoned in modern epistemology.
On what basis is Des Cartes' constraint abandoned?
Is it that Des Cartes constrained justification for knowledge so strictly that skepticism is the only option?
Also, if we are not 100% certain about a matter yet call it "knowledge," then is knowledge a moving target? When we find evidence that goes against what we thought we *knew*, did the truth change?