西魯斯（Syrus）啊，在透過天文學進行預測的方法中，有兩種是最重要且最有效的。第一種，在順序與效力上都居於首位，藉由這種方法，我們得以掌握太陽、月亮與星辰彼此之間，以及它們與地球之間隨時間發生的相對運動相位；第二種方法，則是我們透過這些相位本身的自然特質，來探討它們在其所環繞的事物中所引起的變化。
Of the means of prediction through astronomy, O Syrus, two are the most important and valid. One, which is first both in order and in effectiveness, is that whereby we apprehend the aspects of the movements of sun, moon, and stars in relation to each other and to the earth, as they occur from time to time; the second is that in which by means of the natural character of these aspects themselves we investigate the changes which they bring about in that which they surround.
這之中的第一種方法擁有其獨立的科學（學科），即使不與第二種方法結合以取得結果，其本身也極具追求價值。關於這點，我們已經盡己所能，在其專屬的論著中透過論證的方法向你闡明過了。現在，我們將以適當的自然（物理）方式來說明這第二種、較不具備自足性的方法。如此一來，追求真理的人就絕不會將這第二種方法的見解，與第一種不變科學的確定性相提並論，因為他會將個別事物中物質屬性的軟弱與不可預測性歸因於此（第二種方法）；然而，當我們如此明顯地看出大多數具普遍性質的事件都肇因於包圍著我們的天體時，他也不會放棄在可能性範圍內去進行這類的探究。
The first of these, which has its own science, desirable in itself even though it does not attain the result given by its combination with the second, has been expounded to you as best we could in its own treatise by the method of demonstration. We shall now give an account of the second and less self-sufficient method in a properly physical way, so that one whose aim is the truth might never compare its perceptions with the sureness of the first, unvarying science, for he ascribes to it the weakness and unpredictability of material qualities found in individual things, nor yet refrain from such investigation as is within the bounds of possibility, when it is so evident that most events of a general nature draw their causes from the enveloping heavens.
但是，由於所有難以企及的事物都很容易受到一般大眾的抨擊，而就前面提到的這兩門學科而言，對第一種學科的指控大概只有盲人才提得出來，但針對第二種學科的指控卻有著似是而非的理由——因為它在某些部分的困難度，讓人們以為它完全無法被理解；或者因為人們認為難以逃避已預知的事物，從而將這門學科的目的貶低為毫無用處——因此，在提供關於這個主題的詳細指導之前，我們將嘗試簡要地檢視這類預測在「可能性」與「實用性」上的程度。首先，我們來探討它的可能性。
But since everything that is hard to attain is easily assailed by the generality of men, and in the case of the two before-mentioned disciplines the allegations against the first could be made only by the blind, while there are specious grounds for those levelled at the second — for its difficulty in parts has made them think it completely incomprehensible, or the difficulty of escaping what is known5 has disparaged even its object as useless — we shall try to examine briefly the measure of both the possibility and the usefulness of such prognostication before offering detailed instruction on the subject. First as to its possibility.