What do you really know with certainty?
In this regard, can there be knowledge without certainty?
A sentence such as “I knew for certain that he would come, but he didn't,” for example, is self-contradictory, whereas “I felt certain he would come, but he didn't” is not. It is thus possible to be in a state of knowledge without being certain and to be certain without having knowledge.
Beside this, what is absolute certainty philosophy?
Absolute certainty is belief beyond any possible doubt (not just reasonable doubt or the balance of probabilities). To avoid this conclusion, Descartes argued that he could be absolutely certain of his own existence (summed up in his famous epigram, "Cogito ergo sum" — "I think, therefore I am").
Humans need knowledge, though, and need a basis for accepting knowledge as true. They cannot live constantly doubting every piece of knowledge. To survive, they must be able to accept knowledge as true, and act accordingly. The term certainty is often used to describe knowledge without the possibility of doubt.