It is in the service of inductive logic that much of Lucretius’ startling imagery is invented. The poetic quality of the book is in no sense “purple-patch” work; it is not an adjunct like the Corinthian columns pasted on Roman concrete walls for ornamental purposes. The pictures will always be found to derive from unusually accurate observations of nature so that they may serve their purpose as the starting points of the induction, or, when induction was impracticable, as a basis for some significant analogue. They are so indelibly presented that the argument which they carry cannot be forgotten. To realize their vital function in the argument one has but to recall a few instances of them: the race-horse leaping forward at the gong, the birds that start singing with the first ray of morning light, the flock of pasturing sheep that from a distance seem not to stir, the particles of dust flitting in a shaft of sunlight, the sudden glory of the dawn, the sea gulls screaming over the whitecaps, the cow in the pasture distraught when her calf is taken from her, the fishes swimming about in the yielding water, the gnat that is so light that its weight is not felt, the dog barking at dreams or deceived by an imagined scent. The science is no less precise in such passages because of the vivid naturalism of the descriptions. It is indeed adapted to the Roman mode of thought, for the dry unimaged style of Epicurus, all too readily satisfied with dogmatic abstractions, would have made little impression upon the Romans. One may wonder why it is that, although Lucretius possessed such a clear conception of the processes and tools of inductive logic, so little time was spent in the laboratory experimentation desiderated by Bacon. Our books of logic often assume that man’s processes of thought were recent inventions, as if no one argued deductively till Aristotle, or inductively till Bacon. One might as well assume that no human being used the lens of the eye until some one discovered its existence by dissection. Indeed Nausicaa’s remarks to Ulysses are as well packed with the fruits of penetrating reasoning as the pleas of a Philadelphia lawyer, and the paleolithic savages who made stone axes and fire pistons in the primeval forests employed the same forms of logic as the modern chemist in his laboratory. Lévy-Brühl’s conclusion that the “prelogical man” lived just beyond protohistory is not very convincing to the classicist. What is sometimes called a history of logic is of course not a history of the acquisition of the logical capacity, but a history of the conscious analyses of the processes that have long been in use.