When one wants to re-translate the term ‘practical applicability&’ into Greek, one will probably come up with the word. Literally, it means ‘good use&’ or ‘serviceableness.&’ This word is quite common in philosophical and historical contexts but rarely used in scientific or practical treatises. For example, Aelian, the tactician, uses it to declare that the first rule in tactics is to ‘determine
... [Show full abstract] the number of troops “in a way that is appropriate and serviceable” for (the requirements of) war&'. Aelian means here that the military commander shall not to stick to an abstract or theoretical principle, but act according to the needs of the specific situation, e.g. the time and place of battle. Of course, the meaning of is not limited to ‘practical applicability&’ - the concept that concerns us here - but it is interesting to see that the famous geographer and astronomer Ptolemy (c. AD 150) makes use of this word in the theoretical chapters of his, his Introduction to Geography. The following discussion will try to show what exactly Ptolemy means by this, and why he attaches great importance to the principle of. First of all, it is worth noting here that Ptolemy uses this word thrice in his Geography. This makes the question of its exact meaning and usage all the more important. In 1.6.2 Ptolemy informs his reader why he felt compelled to write a new handbook on geography despite the fact that shortly before him the geographer Marinos of Tyre had already done the same. Now if we saw no defect in his [Marinos’] final composition, we could content ourselves with making the map of the oikoumenē on the basis of these writings alone, without taking any more trouble about it.