This now appears somewhat like certain receipts given by the Stoics for the purpose of discovering right motive forces in regard to virtue. For their principle put generally is this: “Men must live in conformity with nature, _i.e._ with virtue; for to it” (rational) “nature leads us.” That is the highest good, the end of everything—a most important form in Stoic morality, which appears in Cicero as _finis bonorum_ or _summum bonum_. With the Stoics right reason and the securing of it on its own account, is the highest principle. But here, too, we immediately see that we are thereby merely led round in a circle in a manner altogether formal, because virtue, conformity to nature, and reason, are only determined through one another. Virtue consists in living conformably with nature, and what is conformable to nature is virtue. Likewise thought must further determine what is in conformity with nature, but conformity with nature again is that alone which is determined through reason. The Stoics further say, according to Diogenes Laërtius (VII. 87, 88) “To live according to nature is to live according to that which experience teaches us of the laws both of universal nature and of our own nature, by doing nothing which universal law forbids; and that law is the right reason which pervades everything, being the same with Jupiter, the disposer (καθηγεμόνι) of the existing system of things. The virtue of the happy man is when everything occurs according to the harmony of the genius (δαίμονος) of each individual with reference to the will of the disposer of all things.” Thus everything remains as it was in a universal formalism.
We must throughout allow to the Stoics that virtue consists in following thought, _i.e._ the universal law, right reason; anything is moral and right only in as far as a universal end is in it fulfilled and brought into evidence. This last is the substantial, the essential nature of a relationship, and in it we have that which is really in thought alone. The universal which must be the ultimate determination in action, is, however, not abstract, but the universal in this relationship, just as, for example, in property the particular is placed on one side. Because man, as a man of thought and culture, acts according to his perception, he subordinates his impulses and desires to the universal; for they are individual. There is in each human action an individual and particular element; but there is a distinction as to whether the particular as such is solely insisted upon or whether in this particular the universal is secured. It is to the securing of this universal that the energy of Stoicism is directed. But this universal has still no content and is undetermined, and thereby the Stoic doctrines of virtue are incomplete, empty, meaningless and tedious. Virtue indeed is commended in a forcible, lively and edifying manner, but as to what this universal law of virtue is, we have no indications given us.