The authenticity of some of the essays attributed to him has been questioned, and very likely with propriety, but for our purpose it is not important that they should all be by the same author so long as they represent approximately the same period and type of literature. The spurious treatise, _De placitis philosophorum_, we have already considered in the chapter on Galen, to whom it has also been ascribed. The essay _On Rivers and Mountains_ we shall treat by itself in the present chapter. The _De fato_ has also been called spurious.[915] Superstitious content is not a sufficient reason for denying that a treatise is by Plutarch,[916] since he is superstitious in writings of undoubted genuineness and since we have found the leading scientists of the time unable to exclude superstition from their works entirely. Moreover, many of the essays are in the form of conversations expressing the divergent views of different speakers, and it is not always possible to tell which shade of opinion Plutarch himself favors. Suffice it that the views expressed are those of men of education. [Sidenote: Magic in Plutarch.] Plutarch does not specifically discuss magic under that name at any length in any of his essays, but does treat of such subjects as superstition in general, dreams, oracles, demons, number, fate, the craftiness of animals, and other “natural questions.” Certain vulgar forms of magic, at least, were regarded by him with disapproval or incredulity.[917] He rejects as a fiction the statement that the women of Thessaly can draw down the moon by their spells, but thinks that the notion perhaps originated in the fact or story that Aglaonice, daughter of Hegetor, was so skilful in astrology or astronomy as to be able to foresee the occurrence of lunar eclipses, and that she deluded the people into believing that at such times she brought down the moon from heaven by charms and enchantments.[918] Thus we have one more instance of the union of magic and science, this time of pseudo-magic with real science as at other times of magic with pseudo-science. [Sidenote: Essay on superstition.]