Beliefs are based on opinion, knowledge is true and justified: true corresponds to actual reality; objective truth. We have knowledge when we have: a belief, that is true, conclusive (or at least very strong) justification. Global: we can have no knowledge about anything. Local: we can have no knowledge about some particular matter. Usual ground for skepticism: we can"t acquire sufficient justification for our opinions, people have their own truths and justifications. Empiricism: john locke, all ideas originate in experience, knowledge (justification) is based on sensory experience. 91-92: i was thus led to infer that the ground of all our opinions is far more custom and example than any certain knowledge. (pg. 92: descartes wanted to build a foundation for knowing based on his own certainty and reasoning, he wanted to find absolute truths and remove all doubt and uncertainty.