  A demonstration in Aristotle is a syllogism that produces scientific knowledge. Scientific knowledge is knowledge not simply that something is the case, but why it is the case, what causes bring it about. Perhaps we would do better to call it a scientific understanding of the fact known. This means that one may have cognition that something is true which is quite certain without having scientific knowledge, and Aristotle's Posterior Analytics is not a treatise on what we might nowadays call general epistemology. To produce and transmit scientific understanding, Aristotle thought we had to duplicate, in the deductive order of the science, the order of causes found in reality. Just as the causes can be traced back to first causes rooted in the nature of the thing known, so the science must arise from first principles associated with the real definition of the thing known expressing its nature.