Moreover, Plotinos wrote a book on the Incorruptibility of the soul,[603] as Numenius had done;[604] and both authors discuss the incorporeity of qualities.[605] Besides these passages where there is a definite expression of dependence on earlier sources, there are two in which the verbal similarity[606] is striking enough to justify their being considered references: "Besides, no body could subsist without the power of the universal Soul." "Because bodies, according to their own nature, are changeable, inconstant, and infinitely divisible, and nothing unchangeable remains in them, there is evidently need of a principle that would lead them, gather them, and bind them fast together; and this we name soul."[607] This similarity is so striking that it had already been observed and noted by Bouillet. Compare "We consider that all things called essences are composite, and that not a single one of them is simple," with "Numenius, who believes that everything is thoroughly mingled together, and that nothing is simple."[608] 5. UNCERTAIN INDEBTEDNESS OF PLOTINOS. As Plotinos does not give exact quotations and references, it is difficult always to give their undoubted source. As probably Platonic we may mention the passage about the universal Soul taking care of all that is inanimate;[609] and "When one has arrived at individuals, they must be abandoned to infinity."[610] Also other quotations.[611] The line "It might be said that virtues are actualizations,"[612] might be Aristotelian. We also find:[613] "Thus, according to the ancient maxim, 'Courage, temperance, all the virtues, even prudence, are but purifications.'" "That is the reason that it is right to say that the 'soul's welfare and beauty lie in assimilating herself to the divinity.'" This sounds Platonic, but might be Numenian. In this connection it might not be uninteresting to note passages in Numenius which are attributed to Plato, but which are not to be identified: "O Men, the Mind which you dimly perceive is not the First Mind; but before this Mind is another one, which is older and diviner." "That the Good is One."[614] We turn now to thoughts found identically in Plotinos and Numenius, although no textual identity is to be noted. We may group these according to the subject, the universe, and the soul. 6. PARTICULAR SIMILARITIES.