In his 1690 "Essay Concerning Human Understanding," British philosopher and physician John Locke used the Latin term 'tabula rasa' (blank tablet, erased tablet) to describe the educationalist theory that all humans are born with a 'blank' or empty mind—similar to a tablet with no writings on it, we don't have any ideas or thoughts. Everything we know, including our own identity, is determined by our experiences, our senses and our perception.
In the early twentieth century, analytical philosophers Russell and Moore revived the ancient correspondence theory of truth in which a belief, a concept, an idea, a statement or a proposition can only be considered true if it corresponds with the "facts" or with reality. Everything which doesn't correspond with reality can be considered false. For instance, the statement that the grass is green is considered true, simply because of the fact that the grass is, in fact, green. However, one of the main problems of this theory is that it doesn't provide a clear definition of these "facts."