...and men do not think they know a thing till they have grasped the 'why' of it (which is to grasp the primary cause). So clearly we too must do this as regards both coming to be and passing away and every kind of physical change, in order that, knowing their principles, we may try to refer to these principles each of problems.
In one sense, then (1) that out of which a thing comes to be and which persists, is called 'cause'...
In another sense (2) the form or the archetype, i.e. the statement of the essence, and its genera, are called 'causes', and the parts in the definition.
Again (3) the primary source of the change or coming to rest... generally what makes of what is made and what causes change of what is changed.
Again (4) in the sense of end or 'that for the sake of which' a thing is done... "for the sake of" the end...
All causes, both proper and incidental, may be spoken of either as potential or actual... generally stated or complex.
Cause means either what is particular or a genus, or incidental attribute or a genus of that, and these either as a complex or each by itself; and all six either as actual or as potential.
*in short- fixed and unfixed ~BL*
In investigating the cause of each thing it is necessary to seek what is most precise.... generic effects should be assigned to generic causes, particular effects to particular causes... and powers are relative to possible effects, actually operating causes to things which are actually being effected.
from Aristotle "Physics" Bk. II: Ch. 3