[Footnote 28: Analyt. Post. II. xi. p. 94, a. 21-26. Themistius, p. 83: [Greek: ê( ge/nesis ou)=n tou= me/sou kai\ ai)ti/ou tê\n au)tê\n ou)k e)/chei ta/xin e)ph' a(pa/ntôn, a)ll' ou(= me\n prô/tên ô(s e)pi\ tô=n kinêtikô=n, ou(= de\ teleutai/an ô(s e)pi\ tô=n telô=n kai\ ô(=n e(/neka, ou(= d' a(/ma ô(s e)pi\ tô=n o(rismô=n kai\ tou= ti/ ê)=n ei)=nai.]] [Footnote 29: Analyt. Post. II. p. 94, b. 27-p. 95, a. 9.] That the middle term is the Cause, is equally true in respect to _Entia_, _Fientia_, _Præterita_, and _Futura_; only that in respect to _Entia_, the middle term or Cause must be an _Ens_; in respect to _Fientia_ it must be a _Fiens_; in respect to _Præterita_, a _Præteritum_; and in respect to _Futura_, a _Futurum_; that is, in each case, it must be generated at the corresponding time with the major and minor terms in the conclusion.[30] What is the cause of an eclipse of the moon? The cause is, that the earth intervenes between moon and sun; and this is true alike of eclipses past, present, and future. Such an intervention is the essence or definition of a lunar eclipse: the cause is therefore Formal, and cause and effect are simultaneous, occurring at the same moment of time. But in the other three Causes--Material, Efficient, Final--where phenomena are successive and not simultaneous, can we say that the antecedent is cause and the consequent effect, time being, as seems to us, a _continuum_? In cases like this, we can syllogize from the consequent backward to the antecedent; but not from the antecedent forward to the consequent. If the house has been built, we can infer that the foundations have been laid; but, if the foundations have been laid, we cannot infer that the house has been built.[31] There must always be an interval of time during which inference from the antecedent will be untrue; perhaps, indeed, it may never become true. Cause and _causatum_ in these three last varieties of Cause, do not universally and necessarily reciprocate with each other, as in the case of the Formal cause. Though time is continuous, events or generations are distinct points marked in a continuous line, and are not continuous with each other.[32] The number of these points that may be taken is indeed infinite; yet we must assume some of them as ultimate and immediate _principia_, in order to construct our syllogism, and provide our middle term.[33] Where the middle term reciprocates and is co-extensive with the major and the minor, in such cases we have generation of phenomena in a cycle; _e.g._, after the earth has been made wet, vapour rises of necessity: hence comes a cloud, hence water; which again falls, and the earth again becomes wet.[34] Finally, wherever our conclusion is not universally and necessarily true, but true only in most cases, our immediate _principia_ must also be of the same character, true in most cases, but in most cases only.[35]