The alchemist R.A. Schwaller de Lubicz talked about two types of knowledge, explicit and implicit. Explicit knowledge is concerned with the world, the material, the facts. it is actually the basis of the Scientific Method. Implicit knowledge is that which we, as individuals, draw up fro the sum total of our experiences. For instance take the sentence
This Statement is false.
Explicitly, it is a group of words that delivers a message. On the other hand, explicitly, it is a paradox, and cannot be resolved. Implicitly, we can see it is a paradox almost immediately, and can disregard the statement as impossible. Now while for a human consciousness this seems simple and obvious, for a machine it is a real problem. They are apparently unable to view the implicit meaning, and the explicit meaning causes them to go into a logic loop. The Mathematician Kurt Gödel proved that the same problem exists in any form of artificial thought (any system sufficiently powerful enough, in his exact terms).