In a very broad sense praxiology can be considered as a reflection or a methodology on whatever genre of knowledge is related to action or to its result. One of the ancient Greek words that indicates this relation of knowledge with action is called Phronesis, which is generally translated as 'practical wisdom'. According to Aristotle, in its most general meaning ergon is a 'function', a 'task', or a 'finished work'. The Aristotelian chart on praxis should not conceal some conflicting views about action and its cognitive components among some other Greek philosophers before Aristotle's time. The position of the Sophists on the relation between technè and everyday life activities seems clearer. The Sophist considers human language, as it's used in action, as a technè. In general, the 'usage' dimension of the designed objects is studied by a special discipline that is called ergonomics.