15 The activity of the internal principle which produces change or passage from one perception to another may be called Appetition. It is true that desire [l』appetit] cannot always fully attain to the whole perception at which it aims, but it always obtains some of it and attains to new perceptions.

那種產生變化或從一個知覺向另一個知覺的過渡的內在原則的活動被稱作欲求。誠然，欲求不能完全達到它所指向的全部知覺，但他們總會有所收獲並達到新的知覺。

解釋：知覺和欲求是單子的兩個緊密聯系的根本規定。每個被創造的單子都以上帝的全知、全能和全善為其最終欲求目的，但這是不可能徹底達到的，因而每個單子都表現為永不停息的追求和運動。

16. We have in ourselves experience of a multiplicity in simple substance, when we find that the least thought of which we are conscious involves variety in its object. Thus all those who admit that the soul is a simple substance should admit this multiplicity in the Monad; and M. Bayle ought not to have found any difficulty in this, as he has done in his Dictionary, article 『Rorarius.』

當我們在我們所意識到的最細微的念頭中也能發現它包含著一些不同的對象時，我們就在自身體驗到了單純實體中的多樣性。因而所有那些承認靈魂是單純實體的人也應該承認單子中的這種多樣性；貝爾先生也不應該在此發現困難，如他在他的辭典「羅拉留」辭條中所做的那樣。

解釋：在此萊布尼茨以人的意識活動為例，再次論證單子的「一中之多」的特性：人的意識活動本身是「一」，意識活動總是有多樣性的內容則是「多」。

皮埃爾·貝，1647 –1706) ，是法國主張懷疑論的新教神學家在其《歷史與批判詞典》的 「羅拉留」（1485－1556，主張動物有理性）辭條中，以人的理性的軟弱無力這一懷疑主義思想批判了萊布尼茨的理性神學觀點。

17. Moreover, it must be confessed that perception and that which depends upon it are inexplicable on mechanical grounds, that is to say, by means of figures and motions. And supposing there were a machine, so constructed as to think, feel, and have perception, it might be conceived as increased in size, while keeping the same proportions, so that one might go into it as into a mill. That being so, we should, on examining its interior, find only parts which work one upon another, and never anything by which to explain a perception. Thus it is in a simple substance, and not in a compound or in a machine, that perception must be sought for. Further, nothing but this (namely, perceptions and their changes) can be found in a simple substance. It is also in this alone that all the internal activities of simple substances can consist. (Theod. Pref. [E. 474; G. vi. 37].)

此外，必須承認，知覺以及依賴於知覺的東西，不能用機械的原因來解釋，也就是說，不能用形狀和運動來解釋。假設有一架機器，被制作得能夠思想、感受和擁有知覺，想像它在保持同一比例的情況下在尺寸上被放大，以至於人們可以像走進磨坊一樣進入它。在這種情況下，在考察它的內部的時候，我們只能看到一些部分作用於另一部分，而決找不到任何能夠解釋知覺的東西。因此，只能在單純實體中而非在複合物或機器中尋找知覺。況且，在單純實體中能被找到的只有這個（即知覺及其變化）。單純實體的全部內在運動也僅在於此。（參見《神正論》序言，[E. 474; G. vi. 37]）

解釋：萊布尼茨此處的例子是指能夠知覺的機器是不可能存在的，因為作為實體的特性的知覺是一種質的規定，不能用機械論的量的觀點來解釋。

18. All simple substances or created Monads might be called Entelechies, for they have in them a certain perfection (echousi to enteles); they have a certain self-sufficiency (autarkeia) which makes them the sources of their internal activities and, so to speak, incorporeal automata. (Theod. 87.)

所有的單純實體或被創造的單子都可被稱為隱得來希，因為它們自身之內都具有某種完滿性；他們具有某種自足性，使得他們成為自身內在活動的源泉，也就是說，無形體的自動機。（參見《神正論》，第87節）

解釋：「隱得來希」在希臘文中原義指「完滿」、「完整」，亞里斯多德用「隱得來希」一詞表示從潛能到現實的運動，萊布尼茨的「隱得來希」強調單子的圓滿性和自足性，更接近該詞的本義。

單子或「隱得來希」的圓滿性和自足性是有限的，要不然就和上帝沒有區別了。單子為上帝所創造並被賦予了運動的原則，因而每個單子都是自我運動的、自足的，不需要任何外界的影響。

第三部分 單子的等級（第19節—第30節）

19. If we are to give the name of Soul to everything which has perceptions and desires [appetits] in the general sense which I have explained, then all simple substances or created Monads might be called souls; but as feeling [le sentiment] is something more than a bare perception, I think it right that the general name of Monads or Entelechies should suffice for simple substances which have perception only, and that the name of Souls should be given only to those in which perception is more distinct, and is accompanied by memory.

如果我們把靈魂一詞賦予具有我所解釋的一般意義的知覺和欲求的所有事物，那麼所有的單純實體或被創造的單子都可被稱作靈魂；但因為感受包含了比赤裸的知覺更多的東西，所以我同意單子或隱得來希這種一般的名稱對於僅僅具有知覺的單子而言是足夠的，靈魂這一名稱應該被給與那些具有更清晰的知覺、有記憶相伴隨的單子。

解釋：萊布尼茨按知覺的清晰程度把單子分成三個等級：最低級的是赤裸的單子，只具有最含混的無意識的知覺；其次是靈魂（soul）,具有有意識的知覺即感受，有記憶相伴隨；再次是心靈（mind）或精神(spirit),其知覺具有自我意識和理性。