How do you know things? How do you know that you know what you think you know? What is knowledge? How does it work? How do we achieve it? These are the questions of the branch of philosophy known as epistemology. This is the branch of philosophy that concerns truth and knowledge, how we achieve it and what its nature is, and it largely dominated philosophy in the seventeenth and eighteenth centuries.
The reason this became so crucial at that particular moment was because it coincided with the beginning of the scientific revolution. For a long time, there had been a single picture of the universe, a unified sense of how things worked, which in turn gave us a clear idea of how to go about knowing things.
Throughout the whole of the Middle Ages, the prevailing picture of the universe was that it had been created by God for us. God, being benevolent, wants what is best for us, and so he provided us with an owner's manual for human life, an instruction manual for living, which was the Bible. It contained all the information we needed, and it gave us the rules he wanted us to obey.
If you have a book written by an omniscient being, the all-knowing creator of the universe, the creator of humanity. The creator of you who wants what is best for you, then there is simply no better source of knowledge available. The idea of going out to find knowledge for yourself, of thinking things through on your own, when you already have that resource at hand, is absurd. Nothing you could arrive at independently would be a fraction as valuable as the information contained in that book sent to us for precisely that purpose.
It would be like going to a city you have never visited before and, instead of using Google Maps, deciding you are going to reason out where the hotel is simply by looking at the streets. You do not know anything about it, so you cannot use your own reason to figure out where things are. You defer to the authority. You use Google Maps because Google Maps knows where everything is.
In the same way, the Bible was the Google Maps for human life. The rational thing to do, the logical thing to do, is to defer to it, because it possesses the knowledge that you lack.
But during this period, people began to grow dissatisfied with that picture. It started to look like one picture, rather than simply the obvious, inevitable way the universe was. They wanted knowledge that could make life more comfortable and more productive, knowledge that could cure diseases and extend human life. They wanted knowledge that they themselves had come up with. And so that picture began developing cracks, and to replace it, a number of people set about creating an alternative science.
At this time, there was no division between philosophy and science. It was all combined. The word for science was natural philosophy. Figures such as Descartes, Bacon, Galileo, Newton, and Leibniz were all doing science and philosophizing about the nature of science simultaneously. They were playing the game and making up the rules at the same time, which is an awfully tricky position to be in.
They were trying to figure out how we can know things, without yet knowing how to figure that out. If you don't know how to know things, then you don't know how to figure out how to know things either. It was an incredibly disorienting time, and these philosophers had to begin with very, very little.
It is because of what they built that we have the world we live in, that we have the technology we have, that you are able to see me right now.
During this period, the idea of deferring to the expert, deferring to the authority, was the primary notion of the highest epistemological status. It was the highest epistemological quality one could achieve, because you had the highest authority possible. But the philosophers started wanting to know things for themselves. They started to think things through on their own.
One philosopher, at the very beginning of this movement, who insisted on thinking everything through for himself was René Descartes. And when I say everything, I mean everything. He wanted to go back to the very beginning, to start from scratch, and he wanted to bring all of Western civilization with him, to start all knowledge over again from the very beginning.