I looked up the meaning of know, here are ways of looking at it.
"to be aware of the truth or factuality of : be convinced or certain of".
"to recognize the nature of"
" to perceive directly"
"to have experience of"
Depending on where you find the knowing, in truth, nature of, perceiving or experiencing, makes it more or less certain. If knowing is found in truth, it is seen as right or wrong, an absolute. The nature of, experience of and directly perceiving is more open to the understanding that to know is to understand that we experience and perceive in many different ways. The right, wrong or absolute is only understood if we are all experiencing or perceiving the same thing. Finding knowing in truth leads to certainty, where experiencing and perceiving is less certain and more open to understanding others experiences. For me I see certainty is found and lost as I continue to experience and perceive but understanding and respect for differences is always available. . I have thought I knew only to find new knowing. Maybe this is just one of those moments. :)