Aristotle

“ If a want of balance between heat and cold be the cause of the absence of health, a due balance between them must be the cause of its presence. So conversely, if the affirmation be the cause of the presence of a quality the negation is the cause of its absence. ”

“ This syllogism then does not deal with the cause of the phenomenon but with the fact; for the planets are not really near because they do not twinkle, but do not twinkle because they are near. It is also possible to prove the first fact by means of the second, and the demonstration will then be of the cause. ”

“ These superior sciences will be such as differ in essence from the subordinate sciences, and deal merely with abstract forms. Thus mathematics are concerned with forms, and do not deal with any concrete subject ”

“ If the former, the propositions may be immediate and convertible, when we have the demonstration of the cause, or mediate and inconvertible, when we have only the demonstration of the fact. If different sciences are employed, and one is subordinate to the other, the superior gives the Cause, the inferior the Fact. A difference exists between knowing that a fact is and knowing its cause. This may be considered firstly in connection with the same science and from two points of view, viz. ”