With the onset of 1740s Wolff begins his final great task, Jus Naturae, which would eventually consist of eight thick volumes and which is, in a sense, a crowning moment in the progress of his Latin works.
The topic of Wolff's Natural right is a continuation of his earlier books on general practical philosophy – as one might well remember, in the Wolffian tradition natural right was often regarded as an application of the general practical philosophy. Still, in the first volume, Wolff remains in a sense on quite a general level. The topic of this first volume is universal human right, where universal means what concerns all human beings. In other words, the volume is about rights and obligations of every person, no matter what her station in life.
Wolff's general idea is that the idea of an obligation precedes the idea of right. In other words, if there were no obligations, there would be no rights and therefore no jurisdiction. It comes as no surprise that Wolff then states the existence of some primitive obligations – such obligations should be based on the essence of humanity and are therefore applicable to all human beings.
Since these natural obligations are based on the essence of humanity, which is same for all human beings, it then appears that at least when it comes to these obligations, no human being should have any rights that were not rights of other people. This is especially true in the state of nature, where the only obligations are the natural obligations, while in civil state human beings might have made contracts restricting their natural rights.
The content of this universal natural right or law should then be familiar to us already from Wolff's German ethical writings. Particularly, Wolff divides the universal law into three departments, first of which concerns person's obligations towards oneself. This is the strangest part of Wolffian ethics for modern reader, but based on an essential notion of Wolffian practical philosophy – we are obligated to perfect ourselves. This means, firstly, that we should perfect our own soul. In other words, we should perfect our intellect and try to know things as distinctly as possible. We should also perfect our will and learn how to master our sensuous impulses.
Beyond soul, one should also train and care for one's body. As body is for Wolff something different from the soul and something given to it, he thinks it obvious that we cannot by ourselves decide to end its life. Then again, one should provide nourishment for the body, but not too much, since immoderate eating and drinking merely ruins one's body. One should also use medicine to fix bodily problems caused by diseases.
Human beings also have the right to use those external goods, which lie in their power. They can nourish the body, with products of nature, as long as they do not try to use bodies of other human beings for lunch. One has a right to make one's environment clean enough and even beautiful. Human beings can also spend their time manufacturing some raw materials to shape that is more use than the original.
Human beings have obligations not just toward oneself, but also toward other humans and God, Wolff says. Duties toward others seem mostly negative – one should not be rude to anyone, one should not molest anyone, mentally or physically. To put it short, one should not hinder anyone becoming more and more perfect, and in extreme cases, one should even actively help others to perfect themselves.
Duties toward God do not add that much new to the scheme. At most, one should try to have as accurate picture of God's characteristics as possible and thus avoid deism and other heresies. One should also promote the glory of God and lend one' own will for God's purposes. In practice, this means not much more than acting according to natural law.
So much for Wolff's natural law this time, next we shall see what Baumgarten has to say about ethics.