How Do I Know What I Know?

The question of how one knows what he or she knows is one of definition. Objective knowledge is unattainable in nearly every matter, as knowledge is essentially subjective. In these terms I think, like Descartes, that the only thing any consciousness can be fully certain of as an objective truth is its own existence. However, for this question, I define knowledge as a very high degree of certainty of belief in a given thought. Defining it as such, there are myriad sources from which I draw said beliefs. Ethical truths are drawn from biological, evolutionary history of the human species as well as societal expectations and norms. Such ethical truths, as well as other basic things, are the basis upon which an individual operates in society so it’s natural that they are believed with a very high degree of certainty. The other basic things would be simple thoughts that just occur throughout life, from things told to us in school, by parents or other authority figures to the things that we see in the world, on television, the things we read in novels and in text books. I think the only way to adequately describe the source of knowledge for living things is ascribe it to life itself. Basic as it may seem, to be any more specific would be to preclude exploration into every possible means by which beliefs and knowledge are formed. So how do I know what I know? I know what I know because of what I have lived to experience (not to say knowledge is anywhere near strictly experiential.)