What does it mean to know?
This is the question that epistemology seeks to answer. What is knowledge? How does one come to know something? Under what conditions might one be considered to possess knowledge?
These are important questions because they deal with certainty. When you “know” something, that implies a certain amount of certainty on which you can then proceed with actions or further thoughts in a logical structure. The less certain you are, the less stable your logical foundations, and the more hesitant your actions become. Knowledge, and our relative certainty about knowledge, defines how we approach every action we take. So then, it becomes important to reflect on knowledge itself; this discipline is called epistemology.
Let’s use a simple logical formula to simplify the task. Adam (A) knows some thing (X); where X represents any single idea that can be known.
So, under what conditions might it be said that A knows X?
The first condition should be that A believes X. There are no circumstances under which you might know that X is true without believing X is true; so belief is a key component of knowledge. But, of course belief is not enough to secure knowledge because it is very possible for me to believe something that is not true; and we wouldn’t want to say that Cardinal Bellarmine knew that the sun revolved around the earth, or that Galileo knew that ocean tides were caused by the earth’s movement around the sun because both of these ideas are factually incorrect.
So, knowledge implies belief, but also a factual accuracy. Our formula, now becomes:
A knows X whenA believes X, and
X is in fact true.
But what if A does not have adequate grounds to believe X? For instance, what if Alan believes that the earth is round because the arches in our feet can only be compatible with a round globe? Should we say that he knows? Many would say no, that he simply has an uneducated opinion that happens to be correct, but that this does not constitute knowledge.
So, A knows X whenA believes X, and
X is in fact true, and
A has adequate logical grounds for believing X.
This is an extremely basic and, in many ways, overly simplified introductory word on epistemology; but it should suffice to help catch the reader up to speed on the initial phase of the epistemological conversation. The next step will be to ask “What constitutes logical grounds?”
 Donald Palmer “Does The Center Hold?: An Introduction to Western Philosophy” Third Edition, 41; Louis P Pojman “Philosophy: The Pursuit of Wisdom” 5th edition, 141. There are some that would argue that it is possible to know something is true without realizing that you know it, or believing it at a conscious level. I agree, but think that this is more a matter of semantics than an actual disagreement. I would say that at whatever level an idea is known, it is also believed at that same level of consciousness.
 You could say that they “knew” but only in a rhetorical sense as a proof of the strength of their belief, not in the technical sense that they possessed knowledge.
 Pojman “Philosophy: The Pursuit of Wisdom” 138.
 ibid 142.