Plutarch stands in a somewhat different relation to Seneca. He was a little subsequent in date, but there is a sort of parallelism between the two, both in their scientific and their more general interests. Besides the _Physical Causes_, already referred to, Plutarch made a compilation in five Books--at least it goes under his name--of the Tenets of the Philosophers (_Placita Philosophorum_) regarding a vast number of physical, especially astronomical and physiological, subjects. Diels (_op. cit._ 65) scouts the idea of the genuineness of the “wretched epitome,” and assigns it to the middle of the second century. Whether this be so or not does not much affect its value for us. The existence of the work shows the nature of the material which was available in Seneca’s age. The work is a kind of distant echo of Theophrastus’ lost treatise and preserves many opinions of the older philosophers, of which, to say the least of it, we should otherwise have been less fully informed. The parallelism of the _Placita_ to the _Q.N._ will appear from a few of the titles. Books II. and III. of the former reproduce a long array of opinions of Thales, Empedocles, Anaxagoras, Diogenes, Anaximenes, Democritus, Xenophanes, Xenocrates, not to mention Plato, Aristotle, the Pythagoreans, the Stoics, etc., etc., regarding such subjects as Eclipses, the Milky Way, Comets, Earthquakes, Clouds, Winds, Thunder and Lightning, etc., etc. Plutarch also has questions regarding Aratus _Prognostics_, and a Miscellanea of discussions on allied subjects. Of Latin writers two have special bearing on Seneca. Lucretius (95–51 B.C.), in his great poem on Nature (_De Rerum Natura_), has expounded the Epicurean view of the universe. In so far as science is capable of metrical and poetical exposition, he ranks high among scientific writers; while the recent resuscitation of the atomic theory lends special interest to his views. The Romans were always a practical and not a speculative nation, and any deviation from the type, such as Lucretius or Seneca, becomes especially noteworthy and valuable. Numerous parallelisms between them have been brought out in the Commentary and Notes appended to this Translation.