Discusses questions such as, what is knowledge, what qualifies as knowledge, and what does not; what does it mean to say, "I know, I understand," what is truth, and what is certainty? When can we affirm and be certain that -- I know this or that, this or that is a universal truth I can rely upon, and I know that it so because I have a method and at least one criterion to determine that this or that is indeed a universal truth. Furthermore, how do knowledge and understanding compare with belief: Are there evidences so compelling that, in certain cases, propositions of the form 'I know that X' are indeed expressions of knowledge, and in other cases merely expressions of opinions and/or beliefs? Can the words 'belief', 'understanding', and 'knowledge' be used interchangeably? And by the way, what role does reason play in our endeavours to seek knowledge? And what role does human nature play in that endeavour?